nature vs nurture addiction essay

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The Genetic Basis of Addictive Disorders

Francesca ducci.

a Institute of Psychiatry, Psychological Medicine, Kings College, Box P063, De Crespigny Park, London SE5 8AF, UK

David Goldman

b Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rockville, MD 20852, USA

Addictions, including substance use disorders (SUDs), are multistep conditions that, by definition, require exposure to an addictive agent. The wide variety of addictive agents encompasses drugs, foods, sex, video-gaming, and gambling. Any of these agents may lead to an “addicted state” through neurobiologic pathways partially overlapping with those involved in addiction to psychoactive substances. 1 Millions of people are exposed to addictive agents each year, for instance, in the course of medical care for treatment of pain. The vast majority do not become addicted, even if temporary tolerance and dependence are elicited. The probability of initial use and the probability of progression toward a pathologic pattern of use are influenced by intrinsic factors (eg, genotype, sex, age, age at first use, preexisting addictive disorder, or other mental illness), extrinsic factors (eg, drug availability, peer influences social support, childhood adversity, parenting style, socioeconomic status), and the nature of the addictive agent (eg, psychoactive properties, pharmacokinetics, mode of use or administration). The relative importance of these factors varies across the lifespan and at different stages of addiction. For example, peer influences and family environment are most important for exposure and initial pattern of use, whereas genetic factors and psychopathology play a more salient role in the transition to problematic use. 2

In individuals who are vulnerable to addiction, repetitive exposure to the agent induces long-lasting neuroadaptative changes that further promote drug-seeking behaviors and ultimately lead to persistent and uncontrolled patterns of use that constitute addiction. These neuroadaptive changes are the bases for tolerance, craving, and withdrawal and lead to a motivational shift. 3 Motivation to drug-seeking behavior is initially driven by impulsivity and positive reward. In contrast, compulsivity and negative affect dominate the terminal stages of the pathology. Addictions are in a sense “end-stage” diagnoses because at the time diagnosis is made potentially irreversible neuroadaptative change have occurred—changes that were preventable at an early point of the trajectory of the illness.

The use and abuse of legal and illegal psychoactive substances is a worldwide public health priority with repercussions on the individuals, their families, and society. According to the World Health Organization (WHO), alcohol subtracts 69.4 million of disability-adjusted life years (DALYs) 4 ; tobacco, 59.1 million; and illicit drugs, 12.2 million. 5 From an economic perspective, the cost of substance use and SUDs in the United States is approximately $484 billion/year, which is comparable to the cost of diabetes ($131.7 billion/year) and cancer ($171.6 billion/year). 6

Heritability of Addictions

Evidence from family, adoption, and twin studies converges on the relevance of genetic factors in the development of addictions including SUDs and gambling. 7 – 13 Weighted mean heritabilities for addictions computed from several studies of large cohorts of twins are shown in Fig. 1 . 14 Heritability is lowest for hallucinogens (0.39) and highest for cocaine (0.72).

Heritability (weighted means and ranges) of 10 addictive disorders: hallucinogens, cannabis, stimulants, sedatives, opiates, and cocaine dependence or abuse; alcohol dependence; smoking; caffeine consumption or heavy use; pathologic gambling. Weighted heritability ( h 2 ) means were computed using data from large surveys of adult twins. ( Adapted from Goldman D, Oroszi G, Ducci F. The genetics of addictions: uncovering the genes. Nat Rev Genet 2005;6(7):521–32.)

Heritability estimates are usually higher for addiction than for substance use; however, “no pathologic drug use” and “initiation of use” are also heritable, indicating that genetic influences play a role also in initiation. 10 , 12 , 15

Mode of Inheritance

The identification of specific genes and functional loci moderating vulnerability has been challenging because of the genetic complexity of addictive disorders. This complexity derives from multiple sources including incomplete penetrance, phenocopies, variable expressivity, gene–environment interactions, genetic heterogeneity, polygenicity, and epistasis.

Twin studies can to some extent disentangle the roles of genetic heterogeneity and polygenicity–epistasis. As shown in Fig. 2 , 14 under the epistatic model, combinations of genetic variants, each represented as a puzzle piece, determine phenotypes.

Genetic complexity in unrelated individuals: epistasis and heterogeneity. Each risk allele is represented as a puzzle piece of different color or shape. Black circles indicate affected individuals and empty circles denote unaffected individuals. ( Adapted from Gold man D, Oroszi G, Ducci F. The genetics of addictions: uncovering the genes. Nat Rev Genet 2005;6(7):521–32.)

In contrast, under the genetic heterogeneity model, different genetic variants lead to the same phenotype in different individuals, but a single genetic variant can suffice. In twin studies epistasis leads to high monozygotic/dizygotic (MZ/DZ) concordance ratios, as shown in Fig. 3 .

Genetic complexity and twin concordance: epistasis and heterogeneity. Each risk allele is represented as a puzzle piece of different color or shape. Members of twin pairs are represented by squares. Black squares indicate affected individuals and empty squares denote unaffected individuals. ( Adapted from Goldman D, Oroszi G, Ducci F. The genetics of addictions: uncovering the genes. Nat Rev Genet 2005;6(7):521–32.)

Because MZ twins share all alleles and DZ twins only on average half, epistatic models predict higher MZ/DZ concordance ratios. If a multigene combination is required, the MZ/DZ ratio is higher, and it is very high if a multilocus epistatic combination is required. The odds that DZ twins will inherit a combination of alleles is 0.5 raised to the power of the number of alleles involved in the combination, (0.5) n . Multiple combinations may lead to the same phenotype, but for multilocus interactions this is less likely to compensate for the problem of joint probability to produce exactly 2:1 and 4:1 MZ/DZ ratios, as are expected for single alleles acting dominantly or recessively acting on a dichotomous trait, or for multiple alleles additively contributing to a quantitative trait. The MZ/DZ ratio for autism appears to be as high as 50:1, indicating that epistasis is likely. However, the MZ/DZ twin concordance ratios for SUDs ( Fig. 4 ) converge on 2:1, consistent with alleles of individual effect and with the genetic heterogeneity model.

MZ/DZ twin concordance ratios for 10 addictions. MZ/DZ ratios tend to converge on two, inconsistent with the epistatic model (see text). ( Adapted from Goldman D, Oroszi G, Ducci F. The genetics of addictions: uncovering the genes. Nat Rev Genet 2005;6(7):521–32.)

Gene × gene interaction in addiction has been evaluated using identified loci. However, the paucity of such loci identified so far would be insufficient for generalizations. Perhaps only by chance, the few gene × gene interaction studies performed so far in addiction are consistent with the genetic heterogeneity model and gene–gene additivity. In alcoholism, the protective effects of missense variants in ADH1B (Arg48) and ALDH2 (Lys487) are additive, 16 which is perhaps not the expected result because these variants affect consecutive steps in the alcohol metabolic pathway and mediate propensity to alcohol-induced flushing. An additive effect on risk for alcoholism comorbid with other SUDs has been reported for functional loci mapping within the serotonin 3B receptor ( HTR3B ) and serotonin transporter ( SLC6A4 ) genes. 17 , 18 In nicotine addiction, two variants associated with smoking appear to act additively. 19 These nicotine addiction risk variants map in the CHRNA5 – CHRNA3 – CHRNB4 nicotinic acetylcholine receptor subunit cluster and in the TTC12 – ANKK1 – DRD2 cluster, which includes DRD2 , a dopamine receptor important in nicotine reward. In a community sample of 5000 Finns, the alleles most significantly associated with smoking were CHRNA5 Asp398Asn and an intronic variation within TTC12 (rs10502172). Adolescent carriers of three to four risk alleles at these two loci (20% of the population) had a threefold increase in odds of smoking regularly and 2.5-fold increased odds of occasionally smoking as compared to noncarriers, who constitute 9% of the population. Carriers of one or two risk alleles were at intermediate risk. A similar stepwise increase in risk with allele dosage was observed in adulthood, and again consistent with additivity ( Fig. 5 ).

Additive effects of the TTC12–ANKK1–DRD2 and CHRNA5–CHRNA3–CHRNB4 gene clusters on smoking behavior in adolescence and adulthood. Risk of heavy smoking increases linearly with the number of risk alleles at the two loci. Odds ratios (OR) and 95% confidence intervals (CI). ( Adapted from Ducci F, Kaakinen M, Pouta A, et al. TTC12–ANKK1–DRD2 and CHRNA5–CHRNA3–CHRNB4 influence different pathways leading to smoking behavior from adolescence to mid-adulthood. Biol Psychiatry 2011;69(7):650–60.)

The polygenic nature of addiction has implications for the manner in which genetic predictors may eventually be used in treatment and genetic counseling. The loci detected so far, including CHRNA5 Asp398Asn , which has a verified role in smoking, have little predictive value. However, as more genetic risk variants for addiction are discovered and personalized genotyping and sequencing become widespread, there will be increased efforts to use multilocus genetic risk scores to predict vulnerability. 20

Changes in Gene Effects Across the Lifespan

Genetic and environmental influences modulating risk of SUDs change developmentally and across the lifespan. In a longitudinal twin study, Kendler and colleagues 21 found that gene effects in alcohol, cannabis, and nicotine addictions were low in early adolescence but their relative importance gradually grew in adulthood. In contrast, the effect of family environment declined from childhood to adulthood. A possible explanation is that as they mature, people have increasing latitude to shape their choices and social environments, thus increasing the relative importance of genotype. 22 Another explanation is that some genetic factors are important only after repetitive exposure to addictive agents. Also, some alleles may only alter responses of the adult brain. Genetic variation within the CHRNA5 – CHRNA3 – CHRNB4 gene cluster appears to have a stronger effect on smoking behavior in adulthood than in adolescence and moderated the risk of developing a severe pattern of smoking in subjects who had already initiated nicotine use. 19 In contrast, the TTC12 – ANKK1 – DRD2 and MAOA appears to influence personality characteristics such as novelty seeking and impulsivity that promote substance initiation. 19

Shared and Unshared Inheritance

Several addictive disorders tend to co-occur in the same individual. 23 – 25 Studies on genetically informative samples (eg, adoptive or twin studies) can measure the relative contribution of genes and environment to this comorbidity by evaluating the frequency of cross-transmission. 26 Twin studies reveal an overlap between genetic influences for alcoholism and illicit drug use disorders 27 , 28 and between alcoholism and smoking. 29 Kendler and colleagues 30 explored the effect of shared genetic influences on addiction to alcohol, caffeine, nicotine, cannabis, and cocaine in a portion of the Virginia twin sample including 5000 participants. In this study genetic risk could not be explained by one factor acting across all substances. Rather, two shared factors were found: an illicit agent factor mainly explaining vulnerability to cannabis and cocaine dependence and a licit agent factor mainly explaining vulnerability to alcohol, caffeine, and nicotine.

SUDs are frequently comorbid with other mental illnesses including internalizing disorders, such as depression and anxiety, and externalizing disorders, such as conduct disorder (CD), antisocial personality disorder, borderline personality disorder, and attention-deficit/hyperactivity disorder (ADHD). 24 , 25 , 31 Twin studies indicate shared genetic influences between SUDs and externalizing disorders. 27 , 28 , 32 Longitudinal studies have shown that CD and ADHD are important risk factors for addiction. 33 In contrast, twin studies have failed to reveal a shared genetic vulnerability between addiction and internalizing disorder, and it has been suggested that anxiety and depression are more commonly a consequence rather than a risk factor for addiction, being related to neuroadaptation and with drawal. 34 , 35 However, longitudinal studies have shown that some anxiety disorders and anxiety-related personality traits such as panic disorder, social phobia, and increased harm avoidance predict subsequent alcohol problems in adoles cents and young adults. 36

Overall, twin studies predict that genes involved in vulnerability to SUDs include both substance-specific genes and genes that act on common pathways involved in addiction to different agents and propensity to other psychiatric disorders. Substance-specific genes include genes for metabolic enzymes ( ALDH2, ADH1B ) as well as genes encoding gatekeeper molecules such as drug receptors (eg, nicotinic receptors, OPRM1) . On the other hand, genes influencing diverse aspects of addiction neurobiology including anxiety, impulsivity, and reward, including genes such as monoamine oxidase A ( MAOA ), the serotonin transporter ( SLC6A4 ), and catechol- O -methyl transferase ( COMT ), have been implicated in the shared genetic liability between addictions and other psychiatric diseases.

Interplay between Genetic and Enviromental Factors

The gene ( nature ) versus environment ( nurture ) debate represented a misguided and polarizing, dichotomy. Genetic and environmental factors interact in complex ways 37 but there are two main types of violations of gene–environment independence: gene × environment interaction and gene × environment correlation.

Gene × environment correlation (rGE) occurs when genotype correlates (r) with probability of exposure to an environmental factor. Twin studies can address the existence of rGE by measuring the “genetics of the environment.” A gene-based example of rGE is the effect of CHRNA5 Asn398 to increase risk of lung cancer. 38 This functional allele is associated with heavy smoking, thereby leading to increased exposure to carcinogens.

Gene x environment interaction (G × E) occurs when the effect of the environmental exposure on an outcome is modified by genotype (for review see Ref. 39 ). Stressors occurring early in life, such as childhood adversity, are well known risk factors for addiction and comorbid conditions, including antisocial personality disorder (ASPD), CD, borderline personality disorder, and anxiety disorders. However, not all people exposed to early trauma develop psychopathology, indicating differences in resiliency. Functional loci that contribute to interindividual differences in stress resiliency include monoamine oxidase A ( MAOA ), 40 the serotonin transporter ( SLC6A4 ), 41 COMT , 42 the corticotrophin-releasing hormone receptor 1 gene, neuropeptide Y, 43 FKBP5 , 44 the glucocorti coid receptor (GR) gene ( NR3C1 ), 45 and the adenylate cyclase activating poly peptide 1 (pituitary) receptor type gene ( ADCYAP1R1 ). 46

Intermediate Phenotypes

One strategy to discover gene effects in etiologically complex diseases such as addiction is the deconstruction of phenotypes into elements that are etiologically less complex. Intermediate phenotypes access mediating mechanisms of genetic and environmental influences. Heritable intermediate phenotypes that are disease associated are termed endophenotypes. 47

Alcohol-induced flushing is a protective alcohol-related endophenotype influenced by alleles mediating variation in alcohol metabolism. Low response to alcohol is an endophenotype predictive of alcoholism risk. 48 – 50 In humans, level of response is due mainly to pharmacodynamic variation in response 51 rather than variation in metabolism. Low response to alcohol has been associated with genetic variation in the serotonin transporter gene ( SLC6A4 ) and in the gene encoding the subunit a6 of the γ-aminobutyric acid receptor A ( GABRA6 ). 52 Other addiction-relevant intermediate phenotypes include electrophysiologic, neuropsychological, neuroendocrinologic, and, more recently, neuroimaging measures. Neuroimaging accesses neuronal mechanisms underlying emotion, reward, and craving and has thereby enabled linkage of genes to neuronal networks relevant in addiction (for review see Ref. 53 ). For example, amygdala activation after exposure to emotional imagery and stressful stimuli captures interindividual differences in emotional response. 54 As discussed in the text that follows, amygdala activation is influenced by SLC6A4 and MAOA . On the other hand, task-elicited activation of the prefrontal cortex accesses prefrontal cognitive function that is impaired in several psychiatric diseases including addictions and has been linked to genetic variation within COMT and MAOA . Activation of the ventral striatum and other brain areas during positive reward allows exploration of reward circuits 55 enabling the observation that the OPRM1 Asn398Asp variant associated with altered naltrexone treatment response also modulates reward processes in the ventral striatum. 56 Effect sizes of genetic variants on intermediate phenotypes appear to be larger than effects on complex disease phenotypes, potentially reflecting proximity to gene action, measurement properties, and specificity. 43 , 57

Gene Identification

Candidate gene and genome-wide analyses are increasingly integrated to identify genetic variations influencing addiction. In the former, genes known to influence the pathogenesis or treatment of addictions are selected, for example, based on discoveries in animal pharmacobehavioral and genetic studies or based on what is known about the pharmacokinetics and pharmacodynamics of the drug. In genome-wide studies, the genome is interrogated in a hypothesis-free way.

Candidate Genes

Alcohol-metabolizing genes: adh1b and aldh2.

Polymorphisms in the genes encoding for the alcohol-metabolizing enzymes such as the alcohol dehydrogenase IB (ADH1B) and aldehyde dehydrogenase 2 (ALDH2) influence alcohol consumption and risk of alcohol use disorders. ADH1B and ALDH2 catalyze consecutive steps in alcohol metabolism. In adults, these enzymes play an important role although several other enzymes also catalyze these metabolic steps, including catalase, cytochrome P450, and other enzymes in the ADH and ALDH gene families. ADH oxidizes ethanol to acetaldehyde, which is then converted to acetate by ALDH. Acetaldehyde is toxic and adducts with both proteins and DNA. Both acetaldehyde and alcohol are recognized as mutagens. Acetaldehyde is a potent releaser of histamine, and thereby triggers flushing, an aversive reaction characterized by headache, nausea, palpitations, and flushing of the skin. Ordinarily, acetaldehyde is rapidly converted to acetate, and levels of acetaldehyde are very low even after alcohol ingestion. However, if aldehyde dehydrogenase is blocked by disulfiram (a medication used to help alcoholics maintain abstinence) then flushing is observed after ingestion of small quantities of alcohol. The acetaldehyde accumulation can lead to increased risk of upper gastrointestinal (GI) cancer, and cancer risk is greatly augmented by pharmacologic blockade of aldehyde dehydrogenase or natural genetic variation. 58 As shown in Fig. 6 , there are two common enzyme variants of ADH1B and ALDH2 that lead to alcohol-induced flushing, that are protective against alcoholism, and that play a role in the risk of upper GI cancer associated with alcohol consumption ( Fig. 7 ).

Functional polymorphisms in ethanol metabolism: ADH1B His48Arg and ALDH2 Glu487Lys . Higher activity of ADH1B , conferred by Arg48 , or lower activity of ALDH2 , conferred by Lys487 , leads to accumulation of acetaldehyde after alcohol consumption and the flushing reaction.

Geographic distributions of ALDH2 Lys487 and esophageal cancer. The Lys487 allele is highly abundant in Southeast Asia but virtually absent in Europeans, Africans, and Amerindians. Southeast Asia is also an epidemiologic hotspot for esophageal cancer, consistent with genetic epidemiologic studies that have connected risk of esophageal cancer to moderate consumption of alcohol in carriers of the Lys487 allele. Acetaldehyde is a carcinogen. 58 ( Adapted from Li H, Borinskaya S, Yoshimura K, et al. Refined geographic distribution of the oriental ALDH2*504Lys (nee 487Lys) variant. Ann Hum Genet 2009;73(Pt 3):335–45; with permission.)

At the ADH1B His48Arg locus (rs1229984), the His48 allele directly leads to increased catalytic efficiency of ADH1B . Indeed, the rate of oxidation of ethanol to acetaldehyde is increased 100-fold in His48/His48 homozygotes compared to Arg48/Arg48 homozygotes. At the ALDH2 Glu487Lys locus (rs671), the Lys487 allele dominantly inactivates ALDH2. Higher ADH1B activity or lower ALDH2 activity lead to accumulation of acetaldehyde and flushing following consumption of small quantities of alcohol. In East Asian populations in which both His48 and Lys487 are highly abundant, and in Jewish populations in which His48 is abundant, many individuals carry genotypes protective against alcoholism. Recently, the protective effect of the His48 ADH1B variant on alcohol dependence was also demonstrated in European and African populations. 59 Following up the connection of acetaldehyde to mutation, both the ADH1B and ALDH2 flushing alleles have been associated with enhanced risk of cancers of the oropharynx and esophagus. 58 As seen in Fig. 7 , rates of upper GI cancer are higher in parts of the world where the ALDH2 Lys487 allele is abundant.

The ADH1B and ALDH2 polymorphisms are ancient, occurring on characteristic and highly diverged haplotypes. It is unlikely that either generic variant was selected to high frequency to reduce the likelihood of alcoholism after the introduction of alcohol into these populations, which probably occurred well after the spread of the polymorphisms. It has been hypothesized that Arg48 and/or Lys487 were selected to high frequencies in East Asian populations because they alter susceptibility to protozoal infections of the gut, including amebiasis. 60 These infections are sometimes treated with metronidazole, which potently inhibits aldehyde dehydrogenase. 60

Genes-Moderating Monoamines

Monoamines including serotonin (5-hydroxytryptamine, 5-HT), norepinephrine (NE), and dopamine (DA) are modulators of emotionality, cognition, and reward. Therefore, it is unsurprising that genes regulating monoamines such as catechol- O -methylrans-ferase ( COMT) and the serotonin transporter ( SLC6A4 ) have been implicated in vulnerability to several psychiatric diseases, including addictions.

COMT metabolizes dopamine and norepinephrine and others catechols. COMT plays an important role in the regulation of dopamine in the prefrontal cortex, where the dopamine transporter is less expressed. 61 , 62 COMT knockout mice have increased levels of dopamine in this brain region. 63 , 64 The COMT gene has two promoters that control the transcription of two different mRNAs and encode a soluble, cytoplasmic protein (S-COMT) and a membrane-bound form (MB-COMT) which—in humans—has 50 additional amino acid residues at the N-terminus. S-COMT predominates in most tissues, accounting for 95% of total COMT activity. 65 In brain, where MB-COMT activity is much higher, 66 this enzyme is located in the cell body, axons, and dendrites of cortical neurons. 67 Val158Met is a common functional single nucleotide substitution of COMT, 68 replacing methionine for valine at codon 158 of MB-COMT and at codon 108 of S-COMT. Via its effect on enzyme stability 69 , 70 the Met158 allele is three- to fourfold less active. 71 Because of its higher activity, the Val158 allele was predicted to lower dopamine level in the frontal cortex. Congruent with this hypothesis, the Val158 allele has been associated with inefficient frontal lobe function evaluated with different psychological and neuroimaging methodologies. 72 – 74 Also, in a pharmacogenetic study, the COMT inhibitor tolcapone improved executive function in val / val homozygotes, but not in individuals homozygous for the met allele, indicating that this drug might correct the higher COMT activity, and consequent lower dopamine level, of Val carriers. 75 On the other hand, Met158 , although associated with better cognitive performance, is associated with decreased stress resilience and increased anxiety. This allele has been associated with increased anxiety in women, 76 which might be explained because COMT promoters are down-regulated by estrogens. 77 The Met allele has also been associated with increased pain–stress response and a lower pain threshold, 42 , 78 and with increased amygdala reactivity to unpleasant stimuli. 79 Results from studies exploring the association between COMT and addiction are mixed. Some studies failed to find evidence for an associations 80 ; some indicate Val158 as the risk alleles and others indicate the Met158 alleles as the risk allele. The Val158 allele was found to be in excess among methamphetamine, nicotine, and polysubstance addicts. 80 – 82 On the other hand, in addicted populations with high frequencies of internalizing disorders, such as late-onset alcoholics in Finland 83 and Finnish social drinkers, 84 increased risk appeared to be conferred by the Met158 allele.

The serotonin transporter (SLC6A4) regulates synaptic levels of serotonin, a neurotransmitter involved in the regulation of mood, appetite, and impulse control. Reflecting these diverse actions, serotonin-specific reuptake inhibitors are the most commonly prescribed category of medications for mental illness. The serotonin transporter gene SLC6A4 has a common variable number tandem repeat (VNTR) in its promoter region ( HTTLPR ) ( Fig. 8 ) that is the most frequently studied locus in psychiatric genetics.

The serotonin-transporter-linked polymorphic region. The human serotonin transporter promoter has a common VNTR termed HTTLPR . The major alleles within this VNTR, namely L (long) and S (short), differ in number of copies of a 20-bpto23-bp imperfect repeat. The L allele, which leads to increased transcription efficiency, has 16 copies of the repeat and the S allele has 14 copies. Further, a relatively common, functional A > G SNP within the L allele leads to an LG allele functionally equivalent to the S allele. ( Data from Lesch KP, Bengel D, Heils A, et al. Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 1996;274(5292):1527-31; and Hu XZ, Lipsky RH, Zhu G, et al. Serotonin transporter promoter gain-of-function genotypes are linked to obsessive compulsive disorder. Am J Hum Genet 2006;78(5):815–26.)

The major alleles within this VNTR differ in the number of copies of a 20- to 23-bp imperfect repeated sequence. The L allele, which leads to increased transcriptional efficiency, has 16 copies of the repeat and the S allele has 14 copies. 85 Further, there is a relatively common, functional A > G single-nucleotide polymorphism (SNP) within the L allele, 86 the L G allele being equivalent to the S allele in transcriptional efficiency. 86 Further supporting the functional effect of HTTLPR , this locus has been shown to regulate serotonin transporter expression in postmortem brain 87 and in vivo using single-photon emission computed tomography (SPECT) imaging 88 although not in all studies. 89 Low-transcribing HTTLPR genotypes have been inconsistently associated with anxiety, depression, and alcoholism. However, the effects of this locus on complex behavior appear stronger if environmental exposure is also considered. HTTLPR moderated the impact of stressful life events on risk of depression and suicidal behavior. 90 Carriers of the low-transcribing S allele exhibited more depression and suicidality after stressful life events than L individuals with two copies of the allele. 90 Although a meta-analysis failed to support this G × E interaction, 91 other metanalyses have, and multiple lines of evidence support a role for HTTLPR regulation of emotion and response to stress. In particular, HTTLPR has been shown to influence the activity of the amygdala, a brain region that regulates emotional response to environmental changes and that is involved in the pathogenesis of depression and anxiety. Both adults 41 and children 92 carrying the low-activity s allele displayed increased amygdala reactivity to fearful stimuli, reduced amygdala volume, 93 and enhanced functional coupling between the amygdala and the ventro medial prefrontal cortex, 94 a brain region that ordinarily represses amygdala activation. In addition, HTTLPR appears to predict stress-induced cortisolrelease. 95 HTT gene × environment interactions have also been observed in animal models. The rhesus macaque has an orthologous polymorphism (rh- 5HTTLPR) in the promoter region of serotonin transporter gene. In these animals, early life stress exposure led to dyscontrolled behavior and enhanced stress response later in life (for review see Ref. 96 ). Consistent with findings in humans, rh - 5HTTLPR influenced alcohol consumption and stress response, depending on rearing conditions. Carriers of the low-expression serotonin transporter genotype that were separated from their moth ers at an early age displayed higher stress reactivity and ethanol preference. 97 Similarly to humans, 95 the combined effect of rh-HTTLPR and environment on stress reactivity appeared to be mediated by the hypothalamic-pituitary-adrenal (HPA) axis.

Genome-Wide Association Studies

As compared to candidate gene studies, genome-wide association studies (GWAS) have the advantage of covering the entire genome in an hypothesis-free way, and the methodology is powerful for detecting relatively common alleles (minor allele frequency [MAF] >5%) of moderate effect. As discussed later, the impact of less common variants cannot be studied by using the current GWAS arrays and requires sequencing strategies. Another advantage of GWAS is that the same genotyping arrays are obtained in different samples facilitating the combination of results from different studies in meta-analyses. This is a crucial aspect because extremely large study samples are necessary to be able to detect the small effects of many common variant on complex diseases. Of note in GWAS, up to 5 million SNPs can be simultaneously tested raising the issue of false positives due to multiple testing. To achieve an effective P value of .05, the genome-wide significance threshold is usually set at approximately 10 −8 .

GWAS for addictions is at a relatively early stage. Several addictions have yet to be evaluated by GWAS and the samples that have been studied thus far have either not been very large (<10,000), or have been flawed by cross-site or cross-country heterogeneity, less than optimal phenotyping, and an insufficient number of subjects with extreme phenotypes. So far, the strongest, and confirmed, locus detected by GWAS is for the CHRNA5-CHRNA3-CHRNB4 gene cluster on chromosome 15q25. 38 , 98 – 102 This region harbors a locus-altering propensity to nicotine addiction. Nicotinic acetylcholine receptors (nAChRs) are pentameric cholinergic receptors that form ligand-gated ion channels. They are key mediators of the effect of nicotine on the central nervous system. Neuronal subtypes of nAChRs include various homomeric or heteromeric combinations of 12 different nicotinic subunits: α2 through α10 and β2 through β4. The CHRNA5-CHRNA3-CHRNB4 gene cluster encodes for the α5, α3, and β4 subunits. Association of genetic variation within this region to smoking behavior was initially discovered using a candidate gene approach 99 , 100 but was subsequently replicated by GWAS. GWAS detect a highly significant peak on chromosome 15q25 corresponding to the region where these three genes are located ( Fig. 9 ).

Association between smoking (number of cigarettes smoked per day, CPD) and genetic variation within the CHRNA5-CHRNA3-CHRNB4 gene-cluster on c15q25. ( A ) In the Manhattan plot, level of significance (–Log P value) of association to SNPs covering 22 autosomes is shown. SNPs reaching genome-wide significance ( P <10 −8 ) are in green. ( B ) The chromosome 15 region contains the CHRNA5-CHRNA3-CHRNB4 gene cluster. ( C ) The most significant SNP within this region is rs1051730, which correlates highly with Asp398Asn. (Data from Liu JZ, Tozzi F, Waterworth DM, et al. Meta-analysis and imputation refines the association of 15q25 with smoking quantity. Nat Genet 2010;42(5):436-40; Hong LE, Gu H, Yang Y, et al. Association of nicotine addiction and nicotine's actions with separate cingulate cortex functional circuits. Arch Gen Psychiatry 2009;66(4):431–41.)

In this region, at least one functional locus responsible for the statistical signal is a nonsynonymous (aspartic acid, Asp [D] to asparagine, Asn [N]; rs16969968) SNP at codon 398 of CHRNA5 . The Asn398 allele has been associated with nicotine dependence/heavy smoking, 99 , 100 pleasurable response to smoking, 101 smoking quantity, 38 smoking persistence, increased susceptibility to develop lung cancer and vascular disease among smokers, 38 , 103 , 104 serum cotinune levels among current smokers, 105 and smoking cessation. 106 According to a recent meta-analysis, each copy of the risk allele accounts only for approximately 0.5% of the variance in number of cigarettes smoked/day, reflecting the crude nature of the phenotype being studied 107 (see Fig. 9C ). Potentially explaining the neural pathways by which the Asp398Asn locus alters propensity to nicotine addiction, the Asn398 allele was found to predict the strength of a brain circuit connecting the anterior cingulate to the ventral striatum 107 ( Fig. 10A ). The anterior cingulate is a component of the limbic system involved in emotional modulation, and the ventral striatum is a principle reward region of the brain. Strength of this circuit itself was associated with smoking status and severity of smoking (see Fig. 10B ), and this genotype predicted the circuit strength in both smokers and nonsmokers. 108

Impact of psychiatric disease status, smoking behavior, and Asp398Asn influence on dorsal anterior cingulate–right ventral striatum functional connectivity. ( A ) Asn398 carriers as compared to Asp398 / Asp398 homozygotes displayed reduced connectivity. Independently from genotype effect, reduced connectivity was also found in smokers (SK) vs nonsmokers (NS) and in psychiatric patients as compared to healthy participants. ( B ) Nicotine craving was negatively correlated with functional connectivity of dorsal anterior cingulate–ventral stria-tum in both smokers with and without psychiatric illnesses. ( Adapted from Hong LE, Hodgkinson CA, Yang Y, et al. A genetically modulated, intrinsic cingulate circuit supports human nicotine addiction. Proc Natl Acad Sci U S A 2010;107(30):13509–14.)

In vitro studies have shown that (α4β2) 2 α5 receptors that differed only by the asparagine 398 amino acid displayed altered response to nicotine agonist compared with receptors containing aspartic acid. 109 Further studies showed that Asn398 lowers Ca permeability and increases short-term desensitization in (α4β2) 2 α5, but does not alter the receptor sensitivity to activation. 110

Other genetic loci implicated by GWAS in smoking behavior include the cyto chrome P450, family 2, subfamily A, polypeptide 6 ( CYP2A6 ). The CYP2A6 enzyme converts nicotine to cotinine and accounts for 70% of initial nicotine metabolism. Functional polymorphisms within CYP2A6 have been associated with number of cigarette smoked per day. Variation within the dopamine β-hydroxylase ( DBH ) gene has been associated with smoking cessation. 111

For alcoholism, GWAS has been even less successful than for smoking. No alcohol dependence GWAS has yielded a finding of genome-wide significance. 97 – 115 A large meta-analysis of GWAS on alcohol consumption was recently conducted in 12 population-based samples of European ancestry, totaling 26,316 individuals. The most significant associated marker, namely rs6943555, mapped to the autism susceptibility candidate 2 gene ( AUTS2 ). Rs6943555 was found to moderate AUTS2 expression in human postmortem brain from the prefrontal cortex. Differences in expression of AUTS2 were found in whole-brain extracts of mice selected for differences in voluntary alcohol consumption. 116 Recently, multiple genome-wide significant loci for resting electroencephalogram (EEG) were identified by GWAS, 117 illustrating the potential power of combining GWAS with the endophenotype strategy. GWAS of neuroimaging responses relevant to addiction such as those exploring impulsivity and reward are under way.

Rare and Common Variants

The focus of genetic studies of addiction, as well as other common disorders, has been common genetic variants with MAF greater than 1%, and usually greater than 5%. The idea behind these studies is the common disease/common variant (CD/CV) hypothesis according to which common alleles of ancient origin and with small to moderate effect lead to susceptibility to common disorders. However, recent evidence suggests that rare variants of stronger effect might substantially contribute to the genetic vulnerability to common diseases (for review see Ref. 118 ). For schizophrenia and autism, multiple risk rare variants with moderate to large effect sizes have been already reported. 119 , 120 Some of these variants appear to be associated with severe forms of disease and are thought to be of recent origin or de novo in sporadic cases. The contribution of rare variants in addictions is largely unknown. However, recent advances in sequencing technologies have opened the way for extensive searches for rare variants. The ability to detect and connect rare variants to behavior can be maximized by the study of genetically related individuals in families and founder populations that offers the advantage of reduced genetic and environmental heterogeneity as compared to mixed outbred populations and by sequencing individuals who are phenotypically extreme.

Rare genetic variants relevant to addiction have been found within the serotonin receptor 2B gene ( HTR2B ) and MAOA , and several of the functional CYP26 alleles are also rare or uncommon. Both HTR2B and MAOA influence impulsivity and behavioral control and findings for these genes in humans remarkably parallel animal models.

MAOA is an X-linked gene encoding monoamine oxidase A, a mitochondrial enzyme that metabolizes monoamine neurotransmitters including norepinephrine, dopamine, and serotonin. MAOA knockout mice have higher levels of serotonin, norepinephrine, and to lesser extent dopamine, and manifest increased aggressive/impulsive behaviour and stress reactivity. 121 In 1993, Brunner and colleagues 122 reported a Dutch pedigree with eight males affected by borderline mental retardation and impulsive behaviors such as aggression, arson, attempted rape, fighting, and exhibitionism ( Fig. 11A ). Affected individuals were hemizygous for a stop-codon in the eighth exon of MAOA leading to a complete and selective deficiency of MAOA activity. Consistently with an X-linked recessive pattern of transmission, heterozygous women were unaffected. This stop codon variant has not been found in other populations. More recently, a common MAOA polymorphism influencing MAOA transcription was discovered. 123 This locus, termed the MAOA -linked polymorphic region ( MAOA-LPR ), is a VNTR located approximately 1.2 kb upstream from the MAOA start codon and within the gene's transcriptional control region 123 (see Fig. 11B ). Alleles at this VNTR have a different number of tandem copies of a 30-bp sequence, with the three- and four-repeat alleles being by far the most common. Alleles with four repeats are transcribed more efficiently than alleles with three copies, leading to higher MAOA enzyme activity. 123

Rare and common MAOA variants. ( A ) Dutch pedigree with eight males affected by Brunner syndrome, X-linked behavioral dyscontrol caused by an MAOA stop codon (C936T). ( B ) The MAOA -linked polymorphic region ( MAOA–LPR ) is a common 30-bp VNTR located approximately 1.2 kb upstream from the MAOA start codon and within the transcriptional control region. The three-repeat allele is transcribed less efficiently, leading to lower MAOA enzyme activity and behavioral consequences. ([ A ] Adapted from Brunner HG, Nelen M, Breakefield XO, et al. Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase A. Science 1993;262(5133):578–80.)

Supporting the in vivo functional impact of this locus. MAOA-LPR was found to predict serotonin 1A receptor availability. 124 In a longitudinally studied cohort of boys, Caspi and colleagues 125 found an interactive effect between MAOA-LPR and childhood adversity on vulnerability to develop conduct disorder, an important risk factor for addiction. In this study, maltreated boys carrying the MAOA low-activity genotype were more likely to develop antisocial problems than boys with the high-activity genotype. This result has been confirmed by a meta-analysis of eight independent studies. 126 Results testing for MAOA × childhood adversity interaction in women are mixed. A recent study conducted in a sample of Native American women with extremely high rates of antisocial personality disorder and exposure to childhood adversity has reported results that parallel those observed in men. In this study, the effect of childhood sexual abuse on risk of developing alcoholism and antisocial personality disorder was influenced by MAOA-LPR genotype. 40 Sexually abused women homozygous for the low-activity MAOA-LPR allele had high rates of both disorders, and heterozygous women displayed an intermediate risk pattern. However, in the absence of childhood sexual abuse, there was no relationship between MAOA genotype and these disorders.

Remarkably, and as was also the case with the serotonin transporter, an orthologous MAOA VNTR is found in the rhesus macaque. As in humans, the lower activity allele predicts aggressive behavior in these animals, and the association is dependent on maternal separation. 127

Interaction between MAOA on risk for antisocial behavior and impulsivity has also been reported for testosterone 128 and alcohol consumption. 129,130

An HTR2B stop codon was linked to severe impulsive aggression, ASPD, and alcoholism, with an effect that appeared to be modulated by stress, alcohol consumption, and hormones. Unlike the MAOA stop codon, the HTR2B stop codon is recurrent, being found in at least 100,000 individuals, but population-restricted.

The HTR2B gene, located on chromosome 2 (2q36.3-q37.1), encodes the sero tonin 2B receptor, a G protein–coupled receptor. Serotonin 2B receptors are widely expressed in the human brain. A rare HTR2B variant, namely Q20 *, is associated with severe impulsivity and criminal violence in the Finnish population. 131 The stop codon has an allele frequency of 1.2% among Finns, but is specific to this founder. The variant was discovered by sequencing individuals displaying extremely severe impulsive and aggressive behavior. The sequencing sample consisted of population-matched controls and violent offenders who underwent psychiatric evaluation for the extreme nature of their crimes (homicides, assaults, arsons). The variant was enriched in individuals with a history of impulsive, nonpremeditated, violence. Carriers of the stop codon who had committed violent crimes did so while inebriated with alcohol, indicating that impulsive aggression could be the result of a HTR2B stop codon by alcohol interaction. Carriers of the stop codon were cognitively within the normal range, except for a potential difference in working memory, which is known to reflect frontal lobe function. In line with studies on humans, mice with the htr2b gene knocked out were more novelty seeking and impulsive. For example, in a delay discounting task, htr2b −/− mice were less able to tolerate delay in order to receive a larger reward. 131

Classification and Treatment of Addictions

Current nosology of addictions limits both clinicians and researchers. The diagnoses are syndromic (based on clusters of symptoms and clinical course rather than etiologically based). 132 In addition, diagnoses are categorical, assuming a cutoff between normal and abnormal, although many of the problems associated with addiction are found in people who fall below the disease-associated threshold. 133 As discussed, twin studies have detected evidence of etiologic factors shared with other psychiatric diseases 28 and linking normal (personality) and abnormal variations (psychopathology). 19 , 32 The identification of specific genes and environmental factors altering vulnerability and ability to recover would seem to represent a first step to develop an etiologically based nosology and to individualize treatment. In this reconceptualization of addiction, neuroimaging and neuropsychological measures would be combined with genotype to help define new diagnostic categories encom-passing both premordid vulnerability and addiction-induced neurobiologic change. Such a sea change in addiction diagnosis and management would require the collection of behavioral and genetic measures and their use against a research foundation that is today largely nonexistent. However, one of the first examples of pharmacogenetic prediction of treatment response in the addictions is a common functional missense variant of the μ-opioid receptor ( OPRM1 Asn40Asp ). As mentioned, this variant also appears to be associated with altered reward function. 56 In several studies, naltrexone, a μ-opioid receptor antagonist, was observed to augment abstinence and good therapeutic outcome in recovering alcoholics. Carriers of the Asp40 allele were highly likely to show clinical improvement when treated with this drug. 134 , 135 Similarly, CHRNA5Asn398Asp 106 and DBH have been reported to influence smoking cessation treatment, and would seem to indicate the existence of subgroups of addicted patients identifiable via genetic testing.

Addictions are common, chronic, and relapsing diseases that develop through a multistep process. The impact of addictions on morbidity and mortality is high worldwide. Twin studies have shown that the heritability of addictions ranges from 0.39 (hallucinogens) to 0.72 (cocaine). Twin studies indicate that genes influence each stage from initiation to addiction, although the genetic determinants may differ. Addictions are by definition the result of gene × environment interaction. These disorders, which are in part volitional, in part inborn, and in part determined by environmental experience, pose the full range of medical, genetic, policy, and moral challenges. Gene discovery is being facilitated by a variety of powerful approaches, but is in its infancy. It is not surprising that the genes discovered so far act in a variety of ways: via altered metabolism of drug (the alcohol and nicotine metabolic gene variants), via altered function of a drug receptor (the nicotinic receptor, which may alter affinity for nicotine but as discussed may also alter circuitry of reward), and via general mechanisms of addiction (genes such as monoamine oxidase A and the serotonin transporter that modulate stress response, emotion, and behavioral control). Addiction medicine today benefits from genetic studies that buttress the case for a neurobiologic origin of addictive behavior, and some general information on familially transmitted propensity that can be used to guide prevention. A few well-validated, specific predictors such as OPRM1 , ADH1B, ALDH2, CHRNA5 , and CYP26 have been identified and can provide some specific guidance, for example, to understand alcohol-related flushing and upper GI cancer risk ( ADH1B and AKLDH2 ), variation in nicotine metabolism ( CYP26 ), and, potentially, naltrexone treatment response ( OPRM1 ). However, the genetic predictors available are few in number and account for only a small portion of the genetic variance in liability, and have not been integrated into clinical nosology or care.

• Addictive disorders are etiologically complex conditions that result from multiple genetic and environmental risk factors. Heritability estimates for addictions range between 0.4 (hallucinogens) to 0.7 (cocaine).
• Genetic and environmental influences modulating risk of substance use disorders change developmentally and across the lifespan.
• Genes involved in vulnerability to addictions include both substance-specific genes and genes that act on common pathways involved in addiction to different agents and propensity to other psychiatric disorders. Substance-specific genes include genes for metabolic enzymes involved in the metabolism of the substance (eg, ALDH2, ADH1B for alcohol) as well as genes encoding gatekeeper molecules such as drug receptors (eg, nicotinic receptors, OPRM1).
• Genes influencing diverse aspects of addiction neurobiology including anxiety, impulsiv-ity, and reward, including genes such as monoamine oxidase A (MAOA), the serotonin transporter (SLC6A4) and catechol-Omethyl transferase (COMT), have been implicated in the shared genetic liability between addictions and other psychiatric diseases.
• At this early stage at which genome-wide association studies have primarily been applied to relatively small addiction samples, more than 95% of the genetic variance remains unaccounted for, indicating that most of the genetic risk factors for addiction have not been discovered yet.
• The identification of the genetic determinants of addiction is important to improve our ability to predict risk, predict treatment response, develop new treatments, and under stand better the effects of the environment. This potential is already exemplified by the use of an OPRM1 variant to predict treatment response to naltrexone in alcoholism.

The authors have nothing to disclose.

Following the people and events that make up the research community at Duke

Nature vs. Nurture and Addiction

By Sarah Haurin

On January 24, 2019

In Behavior/Psychology , Biology , Genetics/Genomics , Lecture , Medicine , Neuroscience

The progressive understanding of addiction as a disease rather than a choice has opened the door to better treatment and research, but there are aspects of addiction that make it uniquely difficult to treat.

One exceptional characteristic of addiction is its persistence even in the absence of drug use: during periods of abstinence, symptoms get worse over time, and response to the drug increases.

Researcher Elizabeth Heller, PhD , of the University of Pennsylvania Epigenetics Institute, is interested in understanding why we observe this persistence in symptoms even after drug use, the initial cause of the addiction, is stopped. Heller, who spoke at a Jan. 18 biochemistry seminar, believes the answer lies in epigenetic regulation.

Epigenetic regulation represents the nurture part of “nature vs. nurture.” Without changing the actual sequence of DNA, we have mechanisms in our body to control how and when cells express certain genes. These mechanisms are influenced by changes in our environment, and the process of influencing gene expression without altering the basic genetic code is called epigenetics.

Heller believes that we can understand the persistent nature of the symptoms of drugs of abuse even during abstinence by considering epigenetic changes caused by the drugs themselves.

To investigate the role of epigenetics in addiction, specifically cocaine addiction, Heller and her team have developed a series of tools to bind to DNA and influence expression of the molecules that play a role in epigenetic regulation, which are called transcription factors. They identified the FosB gene, which has been previously implicated as a regulator of drug addiction, as a site for these changes.

Increased expression of the FosB gene has been shown to increase sensitivity to cocaine, meaning individuals expressing this gene respond more than those not expressing it. Heller found that cocaine users show decreased levels of the protein responsible for inhibiting expression of FosB. This suggests cocaine use itself is depleting the protein that could help regulate and attenuate response to cocaine, making it more addictive.

Another gene, Nr4a1, is important in dopamine signaling, the reward pathway that is “hijacked” by drugs of abuse.  This gene has been shown to attenuate reward response to cocaine in mice. Mice who underwent epigenetic changes to suppress Nr4a1 showed increased reward response to cocaine. A drug that is currently used in cancer treatment has been shown to suppress Nr4a1 and, consequently, Heller has shown it can reduce cocaine reward behavior in mice.

The identification of genes like FosB and Nr4a1 and evidence that changes in gene expression are even greater in periods of abstinence than during drug use. These may be exciting leaps in our understanding of addiction, and ultimately finding treatments best-suited to such a unique and devastating disease.   

Post by undergraduate blogger Sarah Haurin

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What Are Nature vs. Nurture Examples?

How is nature defined, how is nurture defined, the nature vs. nurture debate, nature vs. nurture examples, what is empiricism (extreme nurture position), contemporary views of nature vs. nurture.

Nature vs. nurture is an age-old debate about whether genetics (nature) plays a bigger role in determining a person's characteristics than lived experience and environmental factors (nurture). The term "nature vs. nature" was coined by English naturalist Charles Darwin's younger half-cousin, anthropologist Francis Galton, around 1875.

In psychology, the extreme nature position (nativism) proposes that intelligence and personality traits are inherited and determined only by genetics.

On the opposite end of the spectrum, the extreme nurture position (empiricism) asserts that the mind is a blank slate at birth; external factors like education and upbringing determine who someone becomes in adulthood and how their mind works. Both of these extreme positions have shortcomings and are antiquated.

This article explores the difference between nature and nurture. It gives nature vs. nurture examples and explains why outdated views of nativism and empiricism don't jibe with contemporary views. 

Thanasis Zovoilis / Getty Images

In the context of nature vs. nurture, "nature" refers to genetics and heritable factors that are passed down to children from their biological parents.

Genes and hereditary factors determine many aspects of someone’s physical appearance and other individual characteristics, such as a genetically inherited predisposition for certain personality traits.

Scientists estimate that 20% to 60% percent of temperament is determined by genetics and that many (possibly thousands) of common gene variations combine to influence individual characteristics of temperament.

However, the impact of gene-environment (or nature-nurture) interactions on someone's traits is interwoven. Environmental factors also play a role in temperament by influencing gene activity. For example, in children raised in an adverse environment (such as child abuse or violence), genes that increase the risk of impulsive temperamental characteristics may be activated (turned on).

Trying to measure "nature vs. nurture" scientifically is challenging. It's impossible to know precisely where the influence of genes and environment begin or end.

How Are Inherited Traits Measured?

“Heritability”   describes the influence that genes have on human characteristics and traits. It's measured on a scale of 0.0 to 1.0. Very strong heritable traits like someone's eye color are ranked a 1.0.

Traits that have nothing to do with genetics, like speaking with a regional accent ranks a zero. Most human characteristics score between a 0.30 and 0.60 on the heritability scale, which reflects a blend of genetics (nature) and environmental (nurture) factors.

Thousands of years ago, ancient Greek philosophers like Plato believed that "innate knowledge" is present in our minds at birth. Every parent knows that babies are born with innate characteristics. Anecdotally, it may seem like a kid's "Big 5" personality traits (agreeableness, conscientiousness, extraversion, neuroticism, and openness) were predetermined before birth.

What is the "Big 5" personality traits

The Big 5 personality traits is a theory that describes the five basic dimensions of personality. It was developed in 1949 by D. W. Fiske and later expanded upon by other researchers and is used as a framework to study people's behavior.

From a "nature" perspective, the fact that every child has innate traits at birth supports Plato's philosophical ideas about innatism. However, personality isn't set in stone. Environmental "nurture" factors can change someone's predominant personality traits over time. For example, exposure to the chemical lead during childhood may alter personality.

In 2014, a meta-analysis of genetic and environmental influences on personality development across the human lifespan found that people change with age. Personality traits are relatively stable during early childhood but often change dramatically during adolescence and young adulthood.

It's impossible to know exactly how much "nurture" changes personality as people get older. In 2019, a study of how stable personality traits are from age 16 to 66 found that people's Big 5 traits are both stable and malleable (able to be molded). During the 50-year span from high school to retirement, some traits like agreeableness and conscientiousness tend to increase, while others appear to be set in stone.

Nurture refers to all of the external or environmental factors that affect human development such as how someone is raised, socioeconomic status, early childhood experiences, education, and daily habits.

Although the word "nurture" may conjure up images of babies and young children being cared for by loving parents, environmental factors and life experiences have an impact on our psychological and physical well-being across the human life span. In adulthood, "nurturing" oneself by making healthy lifestyle choices can offset certain genetic predispositions.

For example, a May 2022 study found that people with a high genetic risk of developing the brain disorder Alzheimer's disease can lower their odds of developing dementia (a group of symptoms that affect memory, thinking, and social abilities enough to affect daily life) by adopting these seven healthy habits in midlife:

• Staying active
• Healthy eating
• Losing weight
• Not smoking
• Reducing blood sugar
• Controlling cholesterol
• Maintaining healthy blood pressure

The nature vs. nurture debate centers around whether individual differences in behavioral traits and personality are caused primarily by nature or nurture. Early philosophers believed the genetic traits passed from parents to their children influence individual differences and traits. Other well-known philosophers believed the mind begins as a blank slate and that everything we are is determined by our experiences.

While early theories favored one factor over the other, experts today recognize there is a complex interaction between genetics and the environment and that both nature and nurture play a critical role in shaping who we are.

Eye color and skin pigmentation are examples of "nature" because they are present at birth and determined by inherited genes. Developmental delays due to toxins (such as exposure to lead as a child or exposure to drugs in utero) are examples of "nurture" because the environment can negatively impact learning and intelligence.

In Child Development

The nature vs. nurture debate in child development is apparent when studying language development. Nature theorists believe genetics plays a significant role in language development and that children are born with an instinctive ability that allows them to both learn and produce language.

Nurture theorists would argue that language develops by listening and imitating adults and other children.

In addition, nurture theorists believe people learn by observing the behavior of others. For example, contemporary psychologist Albert Bandura's social learning theory suggests that aggression is learned through observation and imitation.

In Psychology

In psychology, the nature vs. nurture beliefs vary depending on the branch of psychology.

• Biopsychology:  Researchers analyze how the brain, neurotransmitters, and other aspects of our biology influence our behaviors, thoughts, and feelings. emphasizing the role of nature.
• Social psychology: Researchers study how external factors such as peer pressure and social media influence behaviors, emphasizing the importance of nurture.
• Behaviorism: This theory of learning is based on the idea that our actions are shaped by our interactions with our environment.

In Personality Development

Whether nature or nurture plays a bigger role in personality development depends on different personality development theories.

• Behavioral theories: Our personality is a result of the interactions we have with our environment, such as parenting styles, cultural influences, and life experiences.
• Biological theories: Personality is mostly inherited which is demonstrated by a study in the 1990s that concluded identical twins reared apart tend to have more similar personalities than fraternal twins.
• Psychodynamic theories: Personality development involves both genetic predispositions and environmental factors and their interaction is complex.

In Mental Illness

Both nature and nurture can contribute to mental illness development.

For example, at least five mental health disorders are associated with some type of genetic component ( autism ,  attention-deficit hyperactivity disorder (ADHD) ,  bipolar disorder , major depression, and  schizophrenia ).

Other explanations for mental illness are environmental, such as:

• Being exposed to drugs or alcohol in utero 
• Witnessing a traumatic event, leading to post-traumatic stress disorder (PTSD)
• Adverse life events and chronic stress during childhood

In Mental Health Therapy

Mental health treatment can involve both nature and nurture. For example, a therapist may explore life experiences that may have contributed to mental illness development (nurture) as well as family history of mental illness (nature).

At the same time, research indicates that a person's genetic makeup may impact how their body responds to antidepressants. Taking this into consideration is important for finding the right treatment for each individual.

 What Is Nativism (Extreme Nature Position)?

Innatism emphasizes nature's role in shaping our minds and personality traits before birth. Nativism takes this one step further and proposes that all of people's mental and physical characteristics are inherited and predetermined at birth.

In its extreme form, concepts of nativism gave way to the early 20th century's racially-biased eugenics movement. Thankfully, "selective breeding," which is the idea that only certain people should reproduce in order to create chosen characteristics in offspring, and eugenics, arranged breeding, lost momentum during World War II. At that time, the Nazis' ethnic cleansing (killing people based on their ethnic or religious associations) atrocities were exposed.

Philosopher John Locke's tabula rasa theory from 1689 directly opposes the idea that we are born with innate knowledge. "Tabula rasa" means "blank slate" and implies that our minds do not have innate knowledge at birth.

Locke was an empiricist who believed that all the knowledge we gain in life comes from sensory experiences (using their senses to understand the world), education, and day-to-day encounters after being born.

Today, looking at nature vs. nature in black-and-white terms is considered a misguided dichotomy (two-part system). There are so many shades of gray where nature and nurture overlap. It's impossible to tease out how inherited traits and learned behaviors shape someone's unique characteristics or influence how their mind works.

The influences of nature and nurture in psychology are impossible to unravel. For example, imagine someone growing up in a household with an alcoholic parent who has frequent rage attacks. If that child goes on to develop a substance use disorder and has trouble with emotion regulation in adulthood, it's impossible to know precisely how much genetics (nature) or adverse childhood experiences (nurture) affected that individual's personality traits or issues with alcoholism.

Epigenetics Blurs the Line Between Nature and Nurture

"Epigenetics " means "on top of" genetics. It refers to external factors and experiences that turn genes "on" or "off." Epigenetic mechanisms alter DNA's physical structure in utero (in the womb) and across the human lifespan.

Epigenetics blurs the line between nature and nurture because it says that even after birth, our genetic material isn't set in stone; environmental factors can modify genes during one's lifetime. For example, cannabis exposure during critical windows of development can increase someone's risk of neuropsychiatric disease via epigenetic mechanisms.

Nature vs. nurture is a framework used to examine how genetics (nature) and environmental factors (nurture) influence human development and personality traits.

However, nature vs. nurture isn't a black-and-white issue; there are many shades of gray where the influence of nature and nurture overlap. It's impossible to disentangle how nature and nurture overlap; they are inextricably intertwined. In most cases, nature and nurture combine to make us who we are. 

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By Christopher Bergland Christopher Bergland is a retired ultra-endurance athlete turned medical writer and science reporter. 

An Integrated Model of Nature and Nurture Factors that Contribute to Addiction and Recovery

Affiliation.

• 1 Department of Psychology and Behavioral Neurosciences, St. Edward's University, Austin, Texas, USA.
• PMID: 33870829
• DOI: 10.1080/10826084.2021.1901929

Background: In the context of the opioid epidemic and growing awareness of addiction as a public health concern, there are efforts to inform the public, patients, families, and policy makers about the factors that contribute to addiction and facilitate recovery. Several theoretical models provide useful frameworks for this discussion, but each of them has limitations.

Objectives: This paper presents an accessible yet comprehensive theoretical model that integrates empirical evidence about addiction etiology and recovery using the nature-nurture paradigm.

Results: The model presents substance use along a continuum, and identifies risk and protective factors in multiple domains that have been identified by research. The domains on the nature side of the model include genetic and biological factors, comorbid psychiatric and medical disorders, physiological reinforcement of substance use, and changes to neural mechanisms. The domains on the nurture side of the model include sociocultural factors, environmental factors, personality, emotions, cognitions, psychological reinforcement of substance use, and cognitive and behavioral changes. The progression from increased or decreased substance use to addiction or recovery is mediated by changes in neural mechanisms and cognitive and behavioral changes, which have feedback loops with the physiological and psychological reinforcement. Conclusions/Importance : This model is a useful heuristic, consistent with a public health framework, for discussing addiction and recovery with patients, their families, and the public. This integrated model of nature and nurture factors has the potential to inform clinical practice, consultation, research, prevention programs, educational programs, and public policy.

Keywords: Addiction; comorbidity; etiology; recovery; substance use disorder; theoretical model.

• Analgesics, Opioid
• Behavior, Addictive*
• Reinforcement, Psychology
• Substance-Related Disorders*

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Nature vs nurture addiction: understanding dependencies, nature vs nurture addiction: the battle between biology and environment.

Do you ever wonder why some individuals seem more prone to addiction than others? Is it a matter of nature or nurture? The debate surrounding the origins of addiction has raged on for decades, pitting biology against environmental factors. Dubbed the "Nature vs Nurture Addiction" debate, understanding the complex interplay between genetics and upbringing is crucial in comprehending the development of dependencies. In this article, we delve into the intricate relationship between nature and nurture in addiction, exploring the biological and environmental factors that contribute to substance abuse and behavioral addictions.

The Biological Basis of Addiction: Nature’s Role

When it comes to addiction, nature plays a significant role in shaping an individual's susceptibility. Scientists have long recognized that genetics influence a person's predisposition to addiction. Research indicates that certain genes can make individuals more vulnerable to substance abuse and addictive behaviors. The relationship between genetics and addiction is multifaceted, involving various genetic markers and pathways.

One such marker is the Dopamine D2 receptor gene (DRD2), responsible for regulating the brain's reward and pleasure centers. Studies have shown that individuals with a particular variant of this gene may have fewer dopamine receptors, leading to decreased feelings of satisfaction and pleasure. Consequently, individuals with this genetic variant may be more prone to seeking intense rewards through substance use or other addictive behaviors.

In addition to the DRD2 gene, the mu-opioid receptor gene (OPRM1) has also attracted attention from researchers. This gene is involved in the body's response to endorphins, a natural pain-relieving chemical. Variations in the OPRM1 gene can impact an individual's sensitivity to the pleasurable effects of substances like opioids and alcohol, increasing the likelihood of developing an addiction.

While these genetic factors may contribute to an individual's susceptibility to addiction, it is important to note that genetics alone cannot determine one's fate. The influence of environmental factors on addiction must also be considered.

The Impact of Environment: Nurture’s Influence

Nurture, or the environmental factors that shape an individual's upbringing and experiences, plays a crucial role in the development of addiction. While genetics may lay the foundation, it is the environment that often triggers the manifestation of addictive behaviors. Childhood experiences, social interactions, and cultural influences all contribute to an individual's susceptibility to addiction.

Adverse childhood experiences, commonly referred to as ACEs, have been shown to significantly increase the risk of addiction later in life. ACEs encompass various forms of abuse, neglect, and household dysfunction. Children exposed to ACEs are more likely to turn to substance abuse as a coping mechanism, as they may lack healthy coping strategies and emotional support.

Social interactions, particularly peer influence, can also shape an individual's vulnerability to addiction. The pressure to conform and fit in with a certain group can lead individuals to engage in substance abuse or addictive behaviors as a means of acceptance or social validation. Furthermore, cultural factors can influence addiction rates, with certain communities or societies normalizing or glamorizing substance use.

The Interplay Between Nature and Nurture

While nature and nurture are often pitted against each other, it is essential to recognize that addiction is not solely determined by one or the other. In reality, addiction arises from the intricate interplay between genetic predispositions and environmental triggers. Understanding this interaction is crucial in devising effective prevention and treatment strategies.

Imagine a puzzle, with genetics and environment as its two main pieces. Without one piece, the puzzle is incomplete, but together, they form a comprehensive picture of addiction. Genetics may provide the framework, but it is the environmental triggers that complete the puzzle, triggering the onset of addictive behaviors.

Prevention and Treatment: A Comprehensive Approach

Acknowledging the multi-faceted nature of addiction necessitates the implementation of comprehensive prevention and treatment strategies. Simply focusing on one aspect, such as genetics or environment, is insufficient in combating the complexities of addiction.

Prevention efforts should include education about the risks and consequences of substance abuse, targeting both individuals at higher genetic risk and those exposed to adverse environmental factors. By equipping individuals with knowledge and coping skills, we can empower them to make informed decisions and resist the allure of addiction.

Treatment should adopt a holistic approach, addressing both the biological and environmental aspects of addiction. Evidence-based interventions, including cognitive-behavioral therapy, motivational interviewing, and pharmacological approaches, can help individuals overcome their dependencies. Additionally, incorporating supportive environments and addressing underlying trauma or mental health issues is crucial in achieving long-term recovery.

In conclusion, the nature vs nurture addiction debate is a nuanced discussion encompassing the biological and environmental factors that contribute to addiction. While genetics may predispose individuals to addiction, it is the environment that often triggers the manifestation of addictive behaviors. The interplay between nature and nurture is complex, necessitating a comprehensive approach to prevention and treatment. By understanding the intricate relationship between biology and environment, we can make significant strides in combating addiction and supporting individuals on their path to recovery. So, whether it's nature or nurture, let's work together to understand and overcome the dependencies that threaten our well-being.

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The Nature vs. Nurture Debate

Genetic and Environmental Influences and How They Interact

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Verywell / Joshua Seong

• Definitions
• Interaction
• Contemporary Views

Nature refers to how genetics influence an individual's personality, whereas nurture refers to how their environment (including relationships and experiences) impacts their development. Whether nature or nurture plays a bigger role in personality and development is one of the oldest philosophical debates within the field of psychology .

Learn how each is defined, along with why the issue of nature vs. nurture continues to arise. We also share a few examples of when arguments on this topic typically occur, how the two factors interact with each other, and contemporary views that exist in the debate of nature vs. nurture as it stands today.

Nature and Nurture Defined

To better understand the nature vs. nurture argument, it helps to know what each of these terms means.

• Nature refers largely to our genetics . It includes the genes we are born with and other hereditary factors that can impact how our personality is formed and influence the way that we develop from childhood through adulthood.
• Nurture encompasses the environmental factors that impact who we are. This includes our early childhood experiences, the way we were raised , our social relationships, and the surrounding culture.

A few biologically determined characteristics include genetic diseases, eye color, hair color, and skin color. Other characteristics are tied to environmental influences, such as how a person behaves, which can be influenced by parenting styles and learned experiences.

For example, one child might learn through observation and reinforcement to say please and thank you. Another child might learn to behave aggressively by observing older children engage in violent behavior on the playground.

The Debate of Nature vs. Nurture

The nature vs. nurture debate centers on the contributions of genetics and environmental factors to human development. Some philosophers, such as Plato and Descartes, suggested that certain factors are inborn or occur naturally regardless of environmental influences.

Advocates of this point of view believe that all of our characteristics and behaviors are the result of evolution. They contend that genetic traits are handed down from parents to their children and influence the individual differences that make each person unique.

Other well-known thinkers, such as John Locke, believed in what is known as tabula rasa which suggests that the mind begins as a blank slate . According to this notion, everything that we are is determined by our experiences.

Behaviorism is a good example of a theory rooted in this belief as behaviorists feel that all actions and behaviors are the results of conditioning. Theorists such as John B. Watson believed that people could be trained to do and become anything, regardless of their genetic background.

People with extreme views are called nativists and empiricists. Nativists take the position that all or most behaviors and characteristics are the result of inheritance. Empiricists take the position that all or most behaviors and characteristics result from learning.

Examples of Nature vs. Nurture

One example of when the argument of nature vs. nurture arises is when a person achieves a high level of academic success . Did they do so because they are genetically predisposed to elevated levels of intelligence, or is their success a result of an enriched environment?

The argument of nature vs. nurture can also be made when it comes to why a person behaves in a certain way. If a man abuses his wife and kids, for instance, is it because he was born with violent tendencies, or is violence something he learned by observing others in his life when growing up?

Nature vs. Nurture in Psychology

Throughout the history of psychology , the debate of nature vs. nurture has continued to stir up controversy. Eugenics, for example, was a movement heavily influenced by the nativist approach.

Psychologist Francis Galton coined the terms 'nature versus nurture' and 'eugenics' and believed that intelligence resulted from genetics. Galton also felt that intelligent individuals should be encouraged to marry and have many children, while less intelligent individuals should be discouraged from reproducing.

The value placed on nature vs. nurture can even vary between the different branches of psychology , with some branches taking a more one-sided approach. In biopsychology , for example, researchers conduct studies exploring how neurotransmitters influence behavior, emphasizing the role of nature.

In social psychology , on the other hand, researchers might conduct studies looking at how external factors such as peer pressure and social media influence behaviors, stressing the importance of nurture. Behaviorism is another branch that focuses on the impact of the environment on behavior.

Nature vs. Nurture in Child Development

Some psychological theories of child development place more emphasis on nature and others focus more on nurture. An example of a nativist theory involving child development is Chomsky's concept of a language acquisition device (LAD). According to this theory, all children are born with an instinctive mental capacity that allows them to both learn and produce language.

An example of an empiricist child development theory is Albert Bandura's social learning theory . This theory says that people learn by observing the behavior of others. In his famous Bobo doll experiment , Bandura demonstrated that children could learn aggressive behaviors simply by observing another person acting aggressively.

Nature vs. Nurture in Personality Development

There is also some argument as to whether nature or nurture plays a bigger role in the development of one's personality. The answer to this question varies depending on which personality development theory you use.

According to behavioral theories, our personality is a result of the interactions we have with our environment, while biological theories suggest that personality is largely inherited. Then there are psychodynamic theories of personality that emphasize the impact of both.

Nature vs. Nurture in Mental Illness Development

One could argue that either nature or nurture contributes to mental health development. Some causes of mental illness fall on the nature side of the debate, including changes to or imbalances with chemicals in the brain. Genetics can also contribute to mental illness development, increasing one's risk of a certain disorder or disease.

Mental disorders with some type of genetic component include autism , attention-deficit hyperactivity disorder (ADHD), bipolar disorder , major depression , and schizophrenia .

Other explanations for mental illness are environmental. This includes being exposed to environmental toxins, such as drugs or alcohol, while still in utero. Certain life experiences can also influence mental illness development, such as witnessing a traumatic event, leading to the development of post-traumatic stress disorder (PTSD).

Nature vs. Nurture in Mental Health Therapy

Different types of mental health treatment can also rely more heavily on either nature or nurture in their treatment approach. One of the goals of many types of therapy is to uncover any life experiences that may have contributed to mental illness development (nurture).

However, genetics (nature) can play a role in treatment as well. For instance, research indicates that a person's genetic makeup can impact how their body responds to antidepressants. Taking this into consideration is important for getting that person the help they need.

Interaction Between Nature and Nurture

Which is stronger: nature or nurture? Many researchers consider the interaction between heredity and environment—nature with nurture as opposed to nature versus nurture—to be the most important influencing factor of all.

For example, perfect pitch is the ability to detect the pitch of a musical tone without any reference. Researchers have found that this ability tends to run in families and might be tied to a single gene. However, they've also discovered that possessing the gene is not enough as musical training during early childhood is needed for this inherited ability to manifest itself.

Height is another example of a trait influenced by an interaction between nature and nurture. A child might inherit the genes for height. However, if they grow up in a deprived environment where proper nourishment isn't received, they might never attain the height they could have had if they'd grown up in a healthier environment.

A newer field of study that aims to learn more about the interaction between genes and environment is epigenetics . Epigenetics seeks to explain how environment can impact the way in which genes are expressed.

Some characteristics are biologically determined, such as eye color, hair color, and skin color. Other things, like life expectancy and height, have a strong biological component but are also influenced by environmental factors and lifestyle.

Contemporary Views of Nature vs. Nurture

Most experts recognize that neither nature nor nurture is stronger than the other. Instead, both factors play a critical role in who we are and who we become. Not only that but nature and nurture interact with each other in important ways all throughout our lifespan.

As a result, many in this field are interested in seeing how genes modulate environmental influences and vice versa. At the same time, this debate of nature vs. nurture still rages on in some areas, such as in the origins of homosexuality and influences on intelligence .

While a few people take the extreme nativist or radical empiricist approach, the reality is that there is not a simple way to disentangle the multitude of forces that exist in personality and human development. Instead, these influences include genetic factors, environmental factors, and how each intermingles with the other.

Schoneberger T. Three myths from the language acquisition literature . Anal Verbal Behav . 2010;26(1):107-31. doi:10.1007/bf03393086

National Institutes of Health. Common genetic factors found in 5 mental disorders .

Pain O, Hodgson K, Trubetskoy V, et al. Identifying the common genetic basis of antidepressant response . Biol Psychiatry Global Open Sci . 2022;2(2):115-126. doi:10.1016/j.bpsgos.2021.07.008

Moulton C. Perfect pitch reconsidered . Clin Med J . 2014;14(5):517-9 doi:10.7861/clinmedicine.14-5-517

Levitt M. Perceptions of nature, nurture and behaviour . Life Sci Soc Policy . 2013;9:13. doi:10.1186/2195-7819-9-13

Bandura A, Ross D, Ross, SA. Transmission of aggression through the imitation of aggressive models . J Abnorm Soc Psychol. 1961;63(3):575-582. doi:10.1037/h0045925

Chomsky N. Aspects of the Theory of Syntax .

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Watson JB. Behaviorism .

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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Nature Vs. Nurture: Which Makes Us Addicted? Both, Actually

Is drug and alcohol addiction inherited? Or is it caused by environmental factors?

Most people are aware that addiction seems to run in the family, but you have probably also heard that upbringing or stressful circumstances could lead to drug or alcohol dependence. The truth is that both nature (genes) and nurture (environmental factors) cause addiction vulnerability. What’s more, the two realms can combine to increase the risk of addiction further. Addiction is a complex disease, and its causes are unique in each case.

The good news is that nobody is born an addict. Neither will everyone who experiences negative environmental influences become an addict. More good news: effective drug and  alcohol addiction treatment  is available if you are addicted, whether the cause was nature, nurture, or a blend of both. You can overcome drug or alcohol dependence, especially when treatment is individualised and focuses on your unique genetic and environmental factors.

Let’s explore nature and nurture in addiction and look at how you can overcome dependence with personalised treatment in a drug and alcohol rehab centre.

Evolutionary Biology In Addiction

In a way, all humans are genetically predisposed to addiction thanks to our evolution. Humans have learned to prioritise substances or activities that induce pleasure because we are wired to crave pleasure.

It used to make sense the things we find pleasurable today are the things that ensured our species survival back when we were banging rocks together. It is the reason why sweet treats are so addictive. We know too much sugar is bad for us, but our brains make us crave it and forget about the consequences. Why? Because glucose is necessary for fuelling billions of nerve cells in the brain. Sugar was not readily available hundreds of years ago, so our brains rewarded us for making an effort to consume it. We still get that pleasure reward today, even though we can get Reese’s Peanut Butter Cups delivered to our doorstep.

Our brains produce similar feelings of pleasure and gratification when we take drugs. In fact, the anticipation of pleasure and the satisfaction that follows is so powerful that it can completely eclipse the conscious knowledge that drugs are dangerous.

But if we are all wired to crave pleasure, why do some people become addicted to drugs or alcohol while some do not? Let’s dig deeper, first by looking at a famous Hollywood family and their struggles with addiction across multiple generations.

Addiction As a Family Legacy

Drew Barrymore rose to fame after playing the adorable little sister in Spielberg’s E.T.: The Extraterrestrial. Drew is a legendary actress, but she was born into a family dynasty notorious for drug and alcohol addiction.

She called herself a party girl from age eight, smoked cigarettes from age nine, and developed an alcohol addiction by the time she was eleven years old. She was frequently spotted in nightclubs with her mother, Ildiko Jaid Barrymore, before her thirteenth birthday. She developed a fondness for drugs at Studio 54 and the China Club in New York. After turning thirteen, she spent eighteen months in hospital receiving drug and alcohol addiction treatment.

Her father, actor and poet John Barrymore, has a long history of drug arrests and alcohol addiction. Her grandfather, actor John Barrymore, drank himself to death at age sixty. Her Aunt, Diana Barrymore, candidly discussed her drug and alcohol addiction in her best-seller Too Much, Too Soon.

The legacy of addiction passed from generation to generation in the Barrymore family is clear to see. Research backs up the casual observer by showing that children of addicted parents are eight times more likely to abuse substances at some point in their lives than other children.  Scientists have concluded  that a family history of drug disorder is one of the most potent risk factors for the development of drug and/or alcohol addiction. Male children of male alcohol addicts are four to nine times more likely to abuse alcohol than the general population.

Of course, genetics rarely tell the whole story. Members of the same family share the same environment, making it difficult to determine whether genes or nurture is to blame. Drew Barrymore was definitely exposed to adverse environmental factors no twelve year old should be taking drugs with their mum in New York nightclubs. One way scientists isolate the genetic component is by conducting twin and adoption studies.

Twin studies compare identical and non-identical twins to examine the genetic component of addiction vulnerability. Identical twins have 100% matching genes, allowing researchers to find definite links between genetics and addiction. One study found that when one individual in a pair of identical twins was addicted to a substance, there was a high likelihood that the other was also addicted. A correlation exists for non-identical twins, but it is looser.

Adoption studies  show that adoptees are at higher risk of developing a drug or alcohol addiction if their biological parents had an addiction or severe psychiatric illness. In fact, some studies show that adopted babies conceived by addict parents and then raised in sober adoptive homes have the same risk of developing addiction as they would have had if they had stayed with their biological parents.

Genetics in Addiction

You are probably wondering how much genes influence your risk of addiction. According to research, it accounts for 50 to 60 percent of the risk. The keyword here is addiction risk, though addiction itself is never inherited. Only the risk of developing an addiction is inherited. There is no such thing as a born addict.

We inherit genes from our parents. Genes determine our hair and eye colour, our height, and can even influence the way we smile or laugh. You have around 22,333 genes in your body just over twice as many as a fruit fly. More are likely to be found as genome mapping advancements are made. Genetics research shows our vulnerability to addiction is affected by our genes.

Unfortunately, there is no such thing as one addiction gene that could be altered or removed to decrease the risk of addiction. Instead, multiple genes influence vulnerability, including how likely someone is to:

• start using
• enjoy using
• continue using
• feel the consequences of using

Scientists identify addiction genes by finding biological differences that make someone more or less susceptible to addiction. Humans are unreliable for assessing the impact of genetic factors in addiction because we are exposed to so many uncontrollable environmental factors. Scientists use mice instead. Several addiction genes have been catalogued already, including:

• Mice without the serotonin receptor gene Htr1b find cocaine and alcohol more alluring than mice with the gene.
• Mice with a defective Per2 gene drink three times more alcohol than mice with a fully functional Per2 gene.
• Mice with an increased expression of the Mpdz gene experience less severe withdrawal symptoms from barbiturates, which suggests that humans with a decreased expression of this gene find it more difficult to detox from those drugs.

Impulsiveness in Addiction

You know your friend who gets into bar fights? Or that cousin who gets his kicks by making risky financial decisions? Some people’s genes make them more likely to exhibit higher measures of impulsiveness, especially in stressful situations. Impulsive individuals are more likely to act before thinking about consequences, feel invincible, escalate negative behaviours, and struggle to halt a behaviour once it starts.

People with a genetic predisposition to impulsiveness who also have a genetic predisposition to addiction vulnerability are more likely to develop drug or alcohol addiction than the general population.

Here is how that might work: an individual without the serotonin receptor gene Htr1b might find alcohol irresistible. If they are impulsive, too, they might keep drinking after other individuals would choose to stop. You can see how this blend of genes and impulsive behaviour could lead to addiction.

Cross-addiction an Addictive Personality 

Studies have found  evidence that people can inherit a tendency to become addicted to several different substances. People addicted to one substance may be more likely to be addicted to others too because of genetic factors. For example, genome mapping has found that the A1 allele of the dopamine receptor gene DRD2 is more common in people addicted to alcohol and cocaine. The tendency towards addiction to multiple substances is known as cross-addiction.

Cross-addiction can make recovery from addiction particularly tricky. A person recovering from one addiction can become addicted to another substance. The temptation to transfer dependence from one harmful substance to another substance, sex, gambling, exercise, food, or spending money is powerful in cross-addiction situations. It is especially important to seek treatment in a  drug and alcohol rehab centre  in these cases so you can learn how to replace unhealthy behaviour with non-addictive, non-harmful activities.

Can Genes be Changed?

Genetics cannot be changed. You might dye your brown hair blonde, but your genes will always push brown hair out of your head. Addiction genes work in the same way. They will always be present, pushing their own agenda, increasing your risk of abusing drugs or alcohol.

But do not despair. You are not doomed to be an addict if you have a family history of addiction. You can learn how to live healthily with addiction genes during treatment at a drug and alcohol rehab centre. You will find recovery much easier by learning coping strategies from professional counsellors, psychologists, and psychiatrists during therapy.

Nurture In Addiction

Genes are not the whole story in addiction. Factors like lifestyle, upbringing, mental health, demographics, and environment all play a part to influence the likelihood that someone will develop an addiction. Research suggests that nurture contributes 40 to 50 percent of the risk of addiction.

Maybe you thought that if your family has no history of alcohol addiction you can drink with impunity, right? Wrong. Alcohol abuse can lead to dependence whether your genes make you more predisposed to addiction or not. 

Upbringing in Addiction

A child raised by caring authoritative parents is less likely to develop addiction than a child raised by permissive, neglectful, or authoritarian parents.

Authoritative parents praise their children’s accomplishments, guide them towards success, and provide encouragement to improve. The child learns how to problem-solve effectively, regulate their emotions, express themselves maturely, and develop strategies against damaging thoughts that usually appear before substance abuse occurs. Children of authoritative parents are better equipped to make good decisions about drugs or alcohol. Raising a child in this style may offset any genetic predisposition a child has for risk of addiction.

Childhood Trauma in Addiction

The word  trauma  is used to describe emotionally painful negative events that overwhelm a child’s ability to cope. It can include physical abuse, sexual abuse, psychological abuse, and neglect. The National Child Traumatic Stress Network has published data stating that children who experience childhood trauma have higher rates of substance use and abuse. They use drugs or alcohol to self-medicate which, over time, can develop into physical and psychological dependence. The consequences of childhood trauma can be more severe if the child also has addiction genes.

Early Exposure in Addiction

Child and teenage brains are more susceptible to drug and alcohol damage. The earlier a child drinks or uses, the more dangerous it can be.

Peer pressure exacerbates the problem. First, humans are social. We all want to feel like part of a group particularly when we are teens. We might take drugs simply to fit in and have fun. Second, developing brains struggle to consider long-term consequences when instant gratification is readily available. It can be difficult to resist when teenagers are pressured by their friends.

A child’s home-life can increase the risk of addiction, too. Children exposed to drinking in the home are  more likely to drink at a younger age . This could be because parents who give alcohol to their children or drink in front of them inadvertently show that booze is harmless and enjoyable.

Mental Health in Addiction

Mental health disorders like depression, anxiety, and  post-traumatic stress disorder  are all linked to substance abuse. Individuals with poor coping skills tend to become easily upset, blame others, struggle with receiving praise or criticism, isolate themselves, experience enmeshment, or feel social anxiety. These behaviours can lead to a vicious cycle of stress, self-medication to cope with daily life, and finally addiction. If you have an addiction at the same time you are battling a mental health problem, it is important to receive treatment at a drug and alcohol rehab centre that tackles both factors at the same time.

Relationships in Addiction

Ever heard the phrase, You are the company you keep People around us influence us heavily our friends, family, classmates, colleagues, and community. If you have ever felt a strong desire to drink more at an office party or take drugs with your mates in a nightclub just because everyone around you is doing it, you know how powerfully other people’s actions can influence us.

If everyone you know drinks or uses drugs it can be challenging to develop healthy, sober relationships with new people. In a drug and alcohol rehab centre, therapists and psychologists teach how to set reasonable boundaries and form new, healthy relationships.

Nature And Nurture Intertwined

Most addictions develop because of a complex interplay between nature and nurture. There are almost unlimited combinations of ways genes and environmental factors can make you more at risk of drug and alcohol addiction.

Having said that, at-risk genes and harmful environmental factors do not guarantee you will become an addict. People with addiction genes might never develop an addiction. People who experience trauma might never develop an addiction. People who have experienced trauma and have addiction genes might never develop an addiction.

But, if you do develop an addiction, effective drug and alcohol addiction treatment is available. In a drug and alcohol rehab centre, professional staff will determine whether nature, nurture, or a blend of both have shaped your addiction. They will work with you to design a personalised treatment programme based on what they find so you can finally overcome addiction for good.

Treatment To Overcome Addiction at The Dawn Rehab Thailand

While you can never alter your genetic makeup, you can learn how to cope with the genes you have inherited. While you can never erase past trauma, you can learn how to process it and develop strategies to overcome emotional distress and anxiety in the future.

The Dawn is Asia’s leading drug and alcohol rehab centre. We offer affordable, state-of-the-art detox and personalised one-month treatment programmes in the heart of tropical Northern Thailand.

We use the most up-to-date therapies and technologies to treat addiction and  co-occurring mental disorders  like depression, anxiety, and trauma. Our Western-trained counsellors, psychologists, and psychiatrists combine intensive therapies including CBT, MBCT, and MBSR with group counselling and 12-Step support groups to aid your recovery. We also offer cutting-edge transcranial magnetic stimulation therapy in partnership with one of Chiang Ma’s top hospitals to relieve depression and improve mood.

Family Therapy At The Dawn

If your family has a history of addiction, you could benefit from Family Therapy at The Dawn. Dysfunctional relationships can contribute to and perpetuate addiction. Family Therapy counsellors work with you to consider addiction in light of your family’s interactions. Family members who attend therapy with you can learn how to help you gain awareness of your behaviours, learn more about their role in your life, and find ways to strengthen family bonds. They can also work on their own wellbeing, learn how to avoid enabling behaviours, and figure out how to communicate more efficiently. Family members can play a valuable role in your  relapse prevention plan  and help stop substance abuse spreading further within your family.

Contact us for a no-obligation chat  to start your or your loved one’s path to a healthier life today.

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The Truth About Addiction

Nature vs. nurture.

Written By Granite Recovery Centers Clinically Reviewed By Cheryl Smith MS,MLADC May 7, 2021 Nature vs. Nurture is a puzzling topic that has raised serious concern in psychology over decades. The approach is often one-sided, with each side arguing the value of one over the other. It leads to a social debate majorly geared to…

Written By Granite Recovery Centers

Clinically reviewed by cheryl smith ms,mladc.

May 7, 2021

Nature vs. Nurture is a puzzling topic that has raised serious concern in psychology over decades. The approach is often one-sided, with each side arguing the value of one over the other. It leads to a social debate majorly geared to determining the cause of your intelligence.

Philosophers have tried to study and test their effects on human culture, personality, and behavior. They base it on nature describing the genetic traits, behaviors, and dispositions of an individual. It is also through the study of nurture, which relies on the environment, experience, and culture.

The Nature vs. Nurture Debate

The debate of Nature vs. Nurture is a psychological enigma, and philosophers often have different opinions. They suggest that certain traits occur naturally, disregarding change in the environment . Others support that inheritance throughout evolution affects the character and behavioral changes, making you unique from others. But to some, experiences you encountered while growing up contribute to who you are today. It is through learning where you receive training, regardless of your genetic background. It helps you have a specific character, physical attribute, or behavior.

Changes in culture affect the understanding of the debate through the influence of theories of behaviorism. Your strengths and weaknesses link up with your intelligence, and these are based on environmental and genetic factors. The latter affects the brain size, and its biochemistry determines your movements, feelings, and behavior. Your biochemistry also influences the different aspects of cognition that affect thinking, judging, remembering, and solving problems. Addiction is also a question for debate on whether it thrives due to the influence of nurture or nature. Research proves that specific genes affect the taste of alcohol or consumption of drugs, while others show that peer pressure influences it. If you are suffering from a substance use disorder, visit Granite Recovery Centers to receive the best addiction treatment services.

Experiments on Nature vs. Nurture

The debate on Nature vs. Nurture came to life through many experiments centered on the effects of genes and the environment on development. It took philosophers many years to make sense of the matter . Here are some experiments that were tested to answer the nature versus nurture debate.

• Studies of twins: Studies on identical and fraternal twins separated at birth are the most common experiments on Nature vs. Nature. Their similar genetics play a significant role in supporting the fact that nature affects your character, behavior, and intelligence. The bond between identical and fraternal twins causes a similarity in sexual orientation and religiosity.
• The concept of a language-acquisition device: The language-acquisition device tests the influence of genetics and the environment on the production of language. It studies your mental capacity from birth and how you develop to maturity. It does this while focusing on the changes in the environment, experiences, and culture. Its success proved that genetic disposition and changes in the environment contribute to your uniqueness.
• Parenting styles: A study on the influence of parents and guardians played a significant role in the debate. It proves that their behaviors, including etiquette, movement, and reaction when faced with issues, affected a child’s growth. Children learn these through daily observations or via social media and peers.
• Domestication of animals: Domestication of animals focuses on nurturing animals to meet your needs by encouraging domesticated behaviors. These include encouraging a cat or dog to be your companion, feeding sheep and cows for food, and using donkeys for work. It’s through a series of daily activities that leads to successful domestication.

Impact of Nature on Your Health

Genetic inheritance influences your physical and mental health and may change depending on environmental factors. They include common physical traits in the family, a hereditary disease, or an addiction. When suffering from the latter, you need to take up primary treatment in a rehab center before opting for a 12-Step Program to achieve sobriety.

• Effects on physical health: You can also consider maintaining good physical health, especially when you have a hereditary disease. Robust physical health promotes strong bones and muscles, leading to improved health, fitness , and living quality. All these require commitment, patience, and hard work to achieve full recovery. Daily exercise increases your mobility, leading to better functioning of body organs. It strengthens the heart muscles and lowers blood pressure to prevent the development of cardiovascular diseases. You also get to maintain the proper weight that is essential to reducing the risks of being obese. Eating healthy foods reduces cholesterol levels, leading to a lower chance of inheriting stroke or coronary heart disease. Taking foods with less and healthy sugar, and avoiding drugs or alcohol fights genetic diabetes.
• Effects on mental health: Inherited genes can also lead to the development of mental health conditions that may affect your everyday life. Without seeking proper help, it may lead to distress, poor physical health, and an unproductive lifestyle. In extreme situations, it affects your job, relationships, and finances. This can then lead to a stressful life. Bipolar disorder is one of the most likely developed disorders that cause increased restlessness, irritability, and depression . It makes you feel hopeless and sad, leading to a lack of interest in daily activities. In some cases, you experience episodes full of overwhelming happiness, joy, and energy. You may also inherit schizophrenia that causes hallucinations, delusions, and trouble making sense of thoughts. It affects speech delivery, causing you to have low self-esteem.

Effects of Nurture on Your Health

The environment plays a crucial role in nurturing your physical and mental health through the influence of culture and life experiences. They affect your religious beliefs, spoken language, social organizations, lifestyle, and customs around you. It includes your area of residence, climatic conditions, and the type of people interacting with you.

• Effects on physical health: Different places on earth expose you to high chances of having specific physical attributes or illnesses. It includes the type of vegetation surrounding you, lighting in the house, or your friends. Strive to surround yourself with positivity to improve your health and that of those around you. Temperature, altitude, and pollutants also have a significant contribution to your health. Living in cold regions exposes you to common cold or frostbites, while in hot weather, you can get heatstroke or heat cramps. Long-term exposure to polluted air causes loss of lung capacity and later decreased lung function. Poor lighting in the house or room leads to night blindness that occurs after long periods of exposure. It starts with blurry vision, then short-sightedness, and can develop into a cause for concern.
• Effects on mental health: Nurture influences the severity of your behavior, character, and personality developed over time. It depends on whether the environment offers positive or negative energy to determine the development of a condition. You must study an environment before involving or engaging in it. Experiencing bullying or physical abuse in school, at home, or out with people may cause trauma . It may lead to heavy drinking or drug addiction that takes a negative toll on your life. This trauma requires immediate attention, and you’ll need to immerse yourself in an environment that is nurturing and loving.

In cases where the latter is ineffective, try reaching out to a rehab center to receive professional help and guidance. Granite Recovery Centers offers efficient and effective addiction treatment services through our Mental Health Program .

Nature-Based Therapy

Nature-based therapy focuses on genetics and hereditary treatment to relieve or heal a disorder. It involves sharing genetic traits that affect your well-being with a therapist who will not judge nor criticize you.

• Based on genetics: Doctors often inquire whether anyone in your family experienced a disease before beginning treatment. They do this to gauge the root cause of the illness. It helps prevent further damage caused by prescription medication . It helps them advise on the best living habits to aim for with the goal of bettering your condition. The therapy ends up transforming your behavior, health, and emotions into positive outcomes. Your relationships end up being productive both in life and at work. Our therapy can lead to an increase in productivity.
• Based on disposition: A mind is a powerful tool that dictates thoughts, movement, breathing, digestion, and memories. When combined with character, it determines how you relate with those around you. Therapy based on disposition helps reduce negative thoughts and memories that may prevent you from living a positive life. It may require that you spare ample time to ensure you can devote enough time to your therapeutic sessions. Try opening up each time, explaining the root cause of an issue to ensure you benefit from the sessions.

Nurture-Based Therapy

Nurture-based therapy focuses on your beliefs and behaviors based on the immediate environment. It tries to understand where you come from, the behaviors of those around you, and your cultural upbringing. It combines all of these to find an immediate yet effective solution to keep your mind at ease.

• Based on beliefs: Beliefs are entirely dependent on your upbringing, which involves your family, peers, and neighbors. They influence your faith, culture, education, experiences, and mentors in the present and future. Despite this, they do not solely control your decision, though they do affect your decision-making in minor ways. Taking up therapy geared to help you heal from negative beliefs is one of the best things to do in life. It builds your mental health and helps maintain good physical health for a better tomorrow.
• Based on behavior: A range of care with a tailored treatment program aimed at changing negative behavior influences growth. When you accompany it with follow-up options crucial for maintaining good behavior, you can live a positive life. Start by talking to your therapist about the influence of the environment on your behavior. Your therapist may use reinforcements to mold you into exhibiting better behavior. Your therapist may also assign you a mentor or role model who had similar characteristics but changed for the better.

The Interaction Between Nature and Nurture

Focusing on one element over the other does not help in realizing both potentials. Instead, it’s better to prioritize all of them in equal measures and weigh their supremacy based on facts. It helps you understand the influence of the Nature vs. Nurture debate on your development.

Both of them affect your growth. Without one, the other cannot thrive effectively. It requires that you understand the importance of each and strive to use it to your advantage. Here are some examples of the interaction between heredity and the environment.

• Achieving pitch: Inherited pitch helps you hit notes even without taking up music classes. It can last throughout your lifetime. But achieving high notes will require that you go the extra mile of attending music training or having a personal tutor. It requires that you sacrifice ample time, money, effort, and patience to reach your full potential. You end up having positive results after combining the two, which can then lead to a successful music career. It nurtures you into an all-natural musician who does not require accompaniments.
• Growing in height: Certain families are short due to genetic inheritance that may affect you when in a controlled environment. But environmental factors such as eating healthy meals and exercising will lead to your growth in height over time. It’s not a guarantee that your offspring will inherit your height. The balance of nature and nurture affects your growth in both height and size.

Nature Versus Nurture: Is There a Winner?

Trying to prove which is more dominant between nature and nurture is a futile task that you can’t achieve with ease. It’s because both of them play a significant role in your behavior and character development. Instead of focusing on their differences, it’s better to figure out how they work together to make you unique.

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Cause of Addiction: Nature vs. Nurture

Contributed by: Victoria Walsh (guest contributer)

Researchers will most likely continue this debate long into the future, but this is all the factual information we have to go on for now. When looking at each case of addiction, it is essential to note that every case is different and will have its particular reason for occurring. 

Determining the cause of the addiction is a great way to determine whether or not it is, in fact, nature or nurture. 

Addictions Caused By Nature The American Psychological Association recently reported that an individual’s susceptibility to becoming addicted could be linked to their genes. The biological information passed down from parents has proven to determine the number of factors, from eye color to skin color. 

These genes are responsible for linking family members together and pushing their genetics down the line. Some genes increase the likelihood of addiction and can make a person more susceptible to the disorder. 

When diagnosing a person, there is no one gene to blame for the problem. When it comes to nature and addiction, several genes have the power to work together and can influence whether or not people will become addicted or not. 

For example, some people despise the taste of beer and will therefore be protected from becoming addicted to the substance. Some have an increased sensitivity to the substance due to the above-average density of their taste buds. This enables them to taste a little bit more and can play a role in the addiction process. 

The argument that addiction is down to nature can either be strengthened or contradicted by the fact that alcoholism can be passed down via generations . Some families have members who are alcoholics, and those alcoholics may raise children who also drink excessively. 

Is this genetics, or is it simply down to the fact that they know no better after being raised constantly surrounded by it? 

Addictions Caused by Nurture  As people begin to make their way through life, they develop preferences and habits that may lead them to addiction. Certain events and surroundings can help spark the process and this is the nurture side of the addiction process. 

When its mother is protecting a newborn baby from an abusive and alcoholic father, a certain level of trauma occurs. Living in a chaotic and violent home causes instability in one’s life due to the constant feeling of danger. 

These children develop addiction due to their upbringing and not their genetic makeup. The experiences many have endured and survived can spark an addiction without any help from genetics. 

Early use of a drug can cause irreversible damage to the brain and further feed the addiction until it takes over completely. When the brain is still developing, it is very susceptible to the damage drug use and abuse can incur.

The younger you begin to use drugs, the more damage you begin to cause to the cells and the harder it is for your brain to recover. With early teens, it can be harder to say no to peer pressure, therefore increasing the chances of addiction.

Teenagers and Addiction Teens without peer pressure do not face this problem, and therefore the argument that nurture has a significant impact on the addiction process can be backed up. 

Parents who drink excessively in front of their children may be increasing their child’s chances of becoming addicted. Watching someone you look up to drink in excess signals that it is okay to do the same and slowly form beliefs around alcohol, which could determine how you deal with it in the future.

Addiction is a chronic debilitating disease that can have a severe impact on one’s life. Whether or not addiction is down to nature or nurture, it is crucial to understand its impact on one’s health and relationships. Every case of addiction is unique and should be treated differently. 

The proper treatment will determine what may be triggering the disease and hopefully deal with any trauma or genetic makeup that may be pushing a person to give in to their addiction. 

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Nature vs. Nurture

Reviewed by Psychology Today Staff

The expression “nature vs. nurture” describes the question of how much a person's characteristics are formed by either “nature” or “nurture.” “Nature” means innate biological factors (namely genetics ), while “nurture” can refer to upbringing or life experience more generally.

Traditionally, “nature vs. nurture” has been framed as a debate between those who argue for the dominance of one source of influence or the other, but contemporary experts acknowledge that both “nature” and “nurture” play a role in psychological development and interact in complex ways.

• The Meaning of Nature vs. Nurture
• The Nature-vs.-Nurture Debate
• Identifying Genetic and Environmental Factors

The wording of the phrase “nature vs. nurture” makes it seem as though human individuality— personality traits, intelligence , preferences, and other characteristics—must be based on either the genes people are born with or the environment in which they grew up. The reality, as scientists have shown, is more complicated, and both these and other factors can help account for the many ways in which individuals differ from each other.

The words “nature” and “nurture” themselves can be misleading. Today, “ genetics ” and “environment” are frequently used in their place—with one’s environment including a broader range of experiences than just the nurturing received from parents or caregivers. Further, nature and nurture (or genetics and environment) do not simply compete to influence a person, but often interact with each other; “nature and nurture” work together. Finally, individual differences do not entirely come down to a person’s genetic code or developmental environment—to some extent, they emerge due to messiness in the process of development as well.

A person’s biological nature can affect a person’s experience of the environment. For example, a person with a genetic disposition toward a particular trait, such as aggressiveness, may be more likely to have particular life experiences (including, perhaps, receiving negative reactions from parents or others). Or, a person who grows up with an inclination toward warmth and sociability may seek out and elicit more positive social responses from peers. These life experiences could, in turn, reinforce an individual’s initial tendencies. Nurture or life experience more generally may also modify the effects of nature—for example, by expanding or limiting the extent to which a naturally bright child receives encouragement, access to quality education , and opportunities for achievement.

Epigenetics—the science of modifications in how genes are expressed— illustrates the complex interplay between “nature” and “nurture.” An individual’s environment, including factors such as early-life adversity, may result in changes in the way that parts of a person’s genetic code are “read.” While these epigenetic changes do not override the important influence of genes in general, they do constitute additional ways in which that influence is filtered through “nurture” or the environment.

Theorists and researchers have long battled over whether individual traits and abilities are inborn or are instead forged by experiences after birth. The debate has had broad implications: The real or perceived sources of a person’s strengths and vulnerabilities matter for fields such as education, philosophy , psychiatry , and clinical psychology. Today’s consensus—that individual differences result from a combination of inherited and non-genetic factors—strikes a more nuanced middle path between nature- or nurture-focused extremes.

The debate about nature and nurture has roots that stretch back at least thousands of years, to Ancient Greek theorizing about the causes of personality. During the modern era, theories emphasizing the role of either learning and experience or biological nature have risen and fallen in prominence—with genetics gaining increasing acknowledgment as an important (though not exclusive) influence on individual differences in the later 20th century and beyond.

“Nature versus nurture” was used by English scientist Francis Galton. In 1874, he published the book English Men of Science: Their Nature and Nurture , arguing that inherited factors were responsible for intelligence and other characteristics.

Genetic determinism emphasizes the importance of an individual’s nature in development. It is the view that genetics is largely or totally responsible for an individual’s psychological characteristics and behavior. The term “biological determinism” is often used synonymously.

The blank slate (or “tabula rasa”) view of the mind emphasizes the importance of nurture and the environment. Notably described by English philosopher John Locke in the 1600s, it proposed that individuals are born with a mind like an unmarked chalkboard and that its contents are based on experience and learning. In the 20th century, major branches of psychology proposed a primary role for nurture and experience , rather than nature, in development, including Freudian psychoanalysis and behaviorism.

Modern scientific methods have allowed researchers to advance further in understanding the complex relationships between genetics, life experience, and psychological characteristics, including mental health conditions and personality traits. Overall, the findings of contemporary studies underscore that with some exceptions—such as rare diseases caused by mutations in a single gene—no one factor, genetic or environmental, solely determines how a characteristic develops.

Scientists use multiple approaches to estimate how important genetics are for any given trait, but one of the most influential is the twin study. While identical (or monozygotic) twins share the same genetic code, fraternal (or dizygotic) twins share about 50 percent of the same genes, like typical siblings. Scientists are able to estimate the degree to which the variation in a particular trait, like extraversion , is explained by genetics in part by analyzing how similar identical twins are on that trait, compared to fraternal twins. ( These studies do have limitations, and estimates based on one population may not closely reflect all other populations.) 

It’s hard to call either “nature” or “nurture,” genes or the environment, more important to human psychology. The impact of one set of factors or the other depends on the characteristic, with some being more strongly related to one’s genes —for instance, autism appears to be more heritable than depression . But in general, psychological traits are shaped by a balance of interacting genetic and non-genetic influences.

Both genes and environmental factors can contribute to a person developing mental illness. Research finds that a major part of the variation in the risk for psychiatric conditions such as autism spectrum disorder, anxiety disorders, depression, and schizophrenia can be attributed to genetic differences. But not all of that risk is genetic, and life experiences, such as early-life abuse or neglect, may also affect risk of mental illness (and some individuals, based on their genetics, are likely more susceptible to environmental effects than others).

Like other psychological characteristics, personality is partly heritable. Research suggests less than half of the difference between people on measures of personality traits can be attributed to genes (one recent overall estimate is 40 percent). Non-genetic factors appear to be responsible for an equal or greater portion of personality differences between individuals. Some theorize that the social roles people adopt and invest in as they mature are among the more important non-genetic factors in personality development.

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Nature vs. Nurture Debate In Psychology

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

The nature vs. nurture debate in psychology concerns the relative importance of an individual’s innate qualities (nature) versus personal experiences (nurture) in determining or causing individual differences in physical and behavioral traits. While early theories favored one factor over the other, contemporary views recognize a complex interplay between genes and environment in shaping behavior and development.

Key Takeaways

• Nature is what we think of as pre-wiring and is influenced by genetic inheritance and other biological factors.
• Nurture is generally taken as the influence of external factors after conception, e.g., the product of exposure, life experiences, and learning on an individual.
• Behavioral genetics has enabled psychology to quantify the relative contribution of nature and nurture concerning specific psychological traits.
• Instead of defending extreme nativist or nurturist views, most psychological researchers are now interested in investigating how nature and nurture interact in a host of qualitatively different ways.
• For example, epigenetics is an emerging area of research that shows how environmental influences affect the expression of genes.

The nature-nurture debate is concerned with the relative contribution that both influences make to human behavior, such as personality, cognitive traits, temperament and psychopathology.

Examples of Nature vs. Nurture

Nature vs. nurture in child development.

In child development, the nature vs. nurture debate is evident in the study of language acquisition . Researchers like Chomsky (1957) argue that humans are born with an innate capacity for language (nature), known as universal grammar, suggesting that genetics play a significant role in language development.

Conversely, the behaviorist perspective, exemplified by Skinner (1957), emphasizes the role of environmental reinforcement and learning (nurture) in language acquisition.

Twin studies have provided valuable insights into this debate, demonstrating that identical twins raised apart may share linguistic similarities despite different environments, suggesting a strong genetic influence (Bouchard, 1979)

However, environmental factors, such as exposure to language-rich environments, also play a crucial role in language development, highlighting the intricate interplay between nature and nurture in child development.

Nature vs. Nurture in Personality Development

The nature vs. nurture debate in personality psychology centers on the origins of personality traits. Twin studies have shown that identical twins reared apart tend to have more similar personalities than fraternal twins, indicating a genetic component to personality (Bouchard, 1994).

However, environmental factors, such as parenting styles, cultural influences, and life experiences, also shape personality.

For example, research by Caspi et al. (2003) demonstrated that a particular gene (MAOA) can interact with childhood maltreatment to increase the risk of aggressive behavior in adulthood.

This highlights that genetic predispositions and environmental factors contribute to personality development, and their interaction is complex and multifaceted.

Nature vs. Nurture in Mental Illness Development

The nature vs. nurture debate in mental health explores the etiology of depression. Genetic studies have identified specific genes associated with an increased vulnerability to depression, indicating a genetic component (Sullivan et al., 2000).

However, environmental factors, such as adverse life events and chronic stress during childhood, also play a significant role in the development of depressive disorders (Dube et al.., 2002; Keller et al., 2007)

The diathesis-stress model posits that individuals inherit a genetic predisposition (diathesis) to a disorder, which is then activated or exacerbated by environmental stressors (Monroe & Simons, 1991).

This model illustrates how nature and nurture interact to influence mental health outcomes.

Nature vs. Nurture of Intelligence

The nature vs. nurture debate in intelligence examines the relative contributions of genetic and environmental factors to cognitive abilities.

Intelligence is highly heritable, with about 50% of variance in IQ attributed to genetic factors, based on studies of twins, adoptees, and families (Plomin & Spinath, 2004).

Heritability of intelligence increases with age, from about 20% in infancy to as high as 80% in adulthood, suggesting amplifying effects of genes over time.

However, environmental influences, such as access to quality education and stimulating environments, also significantly impact intelligence.

Shared environmental influences like family background are more influential in childhood, whereas non-shared experiences are more important later in life.

Research by Flynn (1987) showed that average IQ scores have increased over generations, suggesting that environmental improvements, known as the Flynn effect , can lead to substantial gains in cognitive abilities.

Molecular genetics provides tools to identify specific genes and understand their pathways and interactions. However, progress has been slow for complex traits like intelligence. Identified genes have small effect sizes (Plomin & Spinath, 2004).

Overall, intelligence results from complex interplay between genes and environment over development. Molecular genetics offers promise to clarify these mechanisms. The nature vs nurture debate is outdated – both play key roles.

Nativism (Extreme Nature Position)

It has long been known that certain physical characteristics are biologically determined by genetic inheritance.

Color of eyes, straight or curly hair, pigmentation of the skin, and certain diseases (such as Huntingdon’s chorea) are all a function of the genes we inherit.

These facts have led many to speculate as to whether psychological characteristics such as behavioral tendencies, personality attributes, and mental abilities are also “wired in” before we are even born.

Those who adopt an extreme hereditary position are known as nativists.  Their basic assumption is that the characteristics of the human species as a whole are a product of evolution and that individual differences are due to each person’s unique genetic code.

In general, the earlier a particular ability appears, the more likely it is to be under the influence of genetic factors. Estimates of genetic influence are called heritability.

Examples of extreme nature positions in psychology include Chomsky (1965), who proposed language is gained through the use of an innate language acquisition device. Another example of nature is Freud’s theory of aggression as being an innate drive (called Thanatos).

Characteristics and differences that are not observable at birth, but which emerge later in life, are regarded as the product of maturation. That is to say, we all have an inner “biological clock” which switches on (or off) types of behavior in a pre-programmed way.

The classic example of the way this affects our physical development are the bodily changes that occur in early adolescence at puberty.

However, nativists also argue that maturation governs the emergence of attachment in infancy , language acquisition , and even cognitive development .

Empiricism (Extreme Nurture Position)

At the other end of the spectrum are the environmentalists – also known as empiricists (not to be confused with the other empirical/scientific  approach ).

Their basic assumption is that at birth, the human mind is a tabula rasa (a blank slate) and that this is gradually “filled” as a result of experience (e.g., behaviorism ).

From this point of view, psychological characteristics and behavioral differences that emerge through infancy and childhood are the results of learning.  It is how you are brought up (nurture) that governs the psychologically significant aspects of child development and the concept of maturation applies only to the biological.

For example, Bandura’s (1977) social learning theory states that aggression is learned from the environment through observation and imitation. This is seen in his famous bobo doll experiment (Bandura, 1961).

Also, Skinner (1957) believed that language is learned from other people via behavior-shaping techniques.

Evidence for Nature

• Biological Approach
• Biology of Gender
• Medical Model

Freud (1905) stated that events in our childhood have a great influence on our adult lives, shaping our personality.

He thought that parenting is of primary importance to a child’s development , and the family as the most important feature of nurture was a common theme throughout twentieth-century psychology (which was dominated by environmentalists’ theories).

Behavioral Genetics

Researchers in the field of behavioral genetics study variation in behavior as it is affected by genes, which are the units of heredity passed down from parents to offspring.

“We now know that DNA differences are the major systematic source of psychological differences between us. Environmental effects are important but what we have learned in recent years is that they are mostly random – unsystematic and unstable – which means that we cannot do much about them.” Plomin (2018, xii)

Behavioral genetics has enabled psychology to quantify the relative contribution of nature and nurture with regard to specific psychological traits. One way to do this is to study relatives who share the same genes (nature) but a different environment (nurture). Adoption acts as a natural experiment which allows researchers to do this.

Empirical studies have consistently shown that adoptive children show greater resemblance to their biological parents, rather than their adoptive, or environmental parents (Plomin & DeFries, 1983; 1985).

Another way of studying heredity is by comparing the behavior of twins, who can either be identical (sharing the same genes) or non-identical (sharing 50% of genes). Like adoption studies, twin studies support the first rule of behavior genetics; that psychological traits are extremely heritable, about 50% on average.

The Twins in Early Development Study (TEDS) revealed correlations between twins on a range of behavioral traits, such as personality (empathy and hyperactivity) and components of reading such as phonetics (Haworth, Davis, Plomin, 2013; Oliver & Plomin, 2007; Trouton, Spinath, & Plomin, 2002).

Implications

Jenson (1969) found that the average I.Q. scores of black Americans were significantly lower than whites he went on to argue that genetic factors were mainly responsible – even going so far as to suggest that intelligence is 80% inherited.

The storm of controversy that developed around Jenson’s claims was not mainly due to logical and empirical weaknesses in his argument. It was more to do with the social and political implications that are often drawn from research that claims to demonstrate natural inequalities between social groups.

For many environmentalists, there is a barely disguised right-wing agenda behind the work of the behavioral geneticists.  In their view, part of the difference in the I.Q. scores of different ethnic groups are due to inbuilt biases in the methods of testing.

More fundamentally, they believe that differences in intellectual ability are a product of social inequalities in access to material resources and opportunities.  To put it simply children brought up in the ghetto tend to score lower on tests because they are denied the same life chances as more privileged members of society.

Now we can see why the nature-nurture debate has become such a hotly contested issue.  What begins as an attempt to understand the causes of behavioral differences often develops into a politically motivated dispute about distributive justice and power in society.

What’s more, this doesn’t only apply to the debate over I.Q.  It is equally relevant to the psychology of sex and gender , where the question of how much of the (alleged) differences in male and female behavior is due to biology and how much to culture is just as controversial.

Polygenic Inheritance

Rather than the presence or absence of single genes being the determining factor that accounts for psychological traits, behavioral genetics has demonstrated that multiple genes – often thousands, collectively contribute to specific behaviors.

Thus, psychological traits follow a polygenic mode of inheritance (as opposed to being determined by a single gene). Depression is a good example of a polygenic trait, which is thought to be influenced by around 1000 genes (Plomin, 2018).

This means a person with a lower number of these genes (under 500) would have a lower risk of experiencing depression than someone with a higher number.

The Nature of Nurture

Nurture assumes that correlations between environmental factors and psychological outcomes are caused environmentally. For example, how much parents read with their children and how well children learn to read appear to be related. Other examples include environmental stress and its effect on depression.

However, behavioral genetics argues that what look like environmental effects are to a large extent really a reflection of genetic differences (Plomin & Bergeman, 1991).

People select, modify and create environments correlated with their genetic disposition. This means that what sometimes appears to be an environmental influence (nurture) is a genetic influence (nature).

So, children that are genetically predisposed to be competent readers, will be happy to listen to their parents read them stories, and be more likely to encourage this interaction.

Interaction Effects

However, in recent years there has been a growing realization that the question of “how much” behavior is due to heredity and “how much” to the environment may itself be the wrong question.

Take intelligence as an example. Like almost all types of human behavior, it is a complex, many-sided phenomenon which reveals itself (or not!) in a great variety of ways.

The “how much” question assumes that psychological traits can all be expressed numerically and that the issue can be resolved in a quantitative manner.

Heritability statistics revealed by behavioral genetic studies have been criticized as meaningless, mainly because biologists have established that genes cannot influence development independently of environmental factors; genetic and nongenetic factors always cooperate to build traits. The reality is that nature and culture interact in a host of qualitatively different ways (Gottlieb, 2007; Johnston & Edwards, 2002).

Instead of defending extreme nativist or nurturist views, most psychological researchers are now interested in investigating how nature and nurture interact.

For example, in psychopathology , this means that both a genetic predisposition and an appropriate environmental trigger are required for a mental disorder to develop. For example, epigenetics state that environmental influences affect the expression of genes.

What is Epigenetics?

Epigenetics is the term used to describe inheritance by mechanisms other than through the DNA sequence of genes. For example, features of a person’s physical and social environment can effect which genes are switched-on, or “expressed”, rather than the DNA sequence of the genes themselves.

Stressors and memories can be passed through small RNA molecules to multiple generations of offspring in ways that meaningfully affect their behavior.

One such example is what is known as the Dutch Hunger Winter, during last year of the Second World War. What they found was that children who were in the womb during the famine experienced a life-long increase in their chances of developing various health problems compared to children conceived after the famine.

Epigenetic effects can sometimes be passed from one generation to the next, although the effects only seem to last for a few generations. There is some evidence that the effects of the Dutch Hunger Winter affected grandchildren of women who were pregnant during the famine.

Therefore, it makes more sense to say that the difference between two people’s behavior is mostly due to hereditary factors or mostly due to environmental factors.

This realization is especially important given the recent advances in genetics, such as polygenic testing.  The Human Genome Project, for example, has stimulated enormous interest in tracing types of behavior to particular strands of DNA located on specific chromosomes.

If these advances are not to be abused, then there will need to be a more general understanding of the fact that biology interacts with both the cultural context and the personal choices that people make about how they want to live their lives.

There is no neat and simple way of unraveling these qualitatively different and reciprocal influences on human behavior.

Epigenetics: Licking Rat Pups

Michael Meaney and his colleagues at McGill University in Montreal, Canada conducted the landmark epigenetic study on mother rats licking and grooming their pups.

This research found that the amount of licking and grooming received by rat pups during their early life could alter their epigenetic marks and influence their stress responses in adulthood.

Pups that received high levels of maternal care (i.e., more licking and grooming) had a reduced stress response compared to those that received low levels of maternal care.

Meaney’s work with rat maternal behavior and its epigenetic effects has provided significant insights into the understanding of early-life experiences, gene expression, and adult behavior.

It underscores the importance of the early-life environment and its long-term impacts on an individual’s mental health and stress resilience.

Epigenetics: The Agouti Mouse Study

Waterland and Jirtle’s 2003 study on the Agouti mouse is another foundational work in the field of epigenetics that demonstrated how nutritional factors during early development can result in epigenetic changes that have long-lasting effects on phenotype.

In this study, they focused on a specific gene in mice called the Agouti viable yellow (A^vy) gene. Mice with this gene can express a range of coat colors, from yellow to mottled to brown.

This variation in coat color is related to the methylation status of the A^vy gene: higher methylation is associated with the brown coat, and lower methylation with the yellow coat.

Importantly, the coat color is also associated with health outcomes, with yellow mice being more prone to obesity, diabetes, and tumorigenesis compared to brown mice.

Waterland and Jirtle set out to investigate whether maternal diet, specifically supplementation with methyl donors like folic acid, choline, betaine, and vitamin B12, during pregnancy could influence the methylation status of the A^vy gene in offspring.

Key findings from the study include:

Dietary Influence : When pregnant mice were fed a diet supplemented with methyl donors, their offspring had an increased likelihood of having the brown coat color. This indicated that the supplemented diet led to an increased methylation of the A^vy gene.

Health Outcomes : Along with the coat color change, these mice also had reduced risks of obesity and other health issues associated with the yellow phenotype.

Transgenerational Effects : The study showed that nutritional interventions could have effects that extend beyond the individual, affecting the phenotype of the offspring.

The implications of this research are profound. It highlights how maternal nutrition during critical developmental periods can have lasting effects on offspring through epigenetic modifications, potentially affecting health outcomes much later in life.

The study also offers insights into how dietary and environmental factors might contribute to disease susceptibility in humans.

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Further Information

• Genetic & Environmental Influences on Human Psychological Differences

Evidence for Nurture

• Classical Conditioning
• Little Albert Experiment
• Operant Conditioning
• Behaviorism
• Social Learning Theory
• Bronfenbrenner’s Ecological Systems Theory
• Social Roles
• Attachment Styles
• The Hidden Links Between Mental Disorders
• Visual Cliff Experiment
• Behavioral Genetics, Genetics, and Epigenetics
• Epigenetics
• Is Epigenetics Inherited?
• Physiological Psychology
• Bowlby’s Maternal Deprivation Hypothesis
• So is it nature not nurture after all?

Evidence for an Interaction

• Genes, Interactions, and the Development of Behavior
• Agouti Mouse Study
• Biological Psychology

What does nature refer to in the nature vs. nurture debate?

In the nature vs. nurture debate, “nature” refers to the influence of genetics, innate qualities, and biological factors on human development, behavior, and traits. It emphasizes the role of hereditary factors in shaping who we are.

What does nurture refer to in the nature vs. nurture debate?

In the nature vs. nurture debate, “nurture” refers to the influence of the environment, upbringing, experiences, and social factors on human development, behavior, and traits. It emphasizes the role of external factors in shaping who we are.

Why is it important to determine the contribution of heredity (nature) and environment (nurture) in human development?

Determining the contribution of heredity and environment in human development is crucial for understanding the complex interplay between genetic factors and environmental influences. It helps identify the relative significance of each factor, informing interventions, policies, and strategies to optimize human potential and address developmental challenges.

Home — Essay Samples — Nursing & Health — Drug Addiction — Nature Vs Nurture In Relation To Drug Addiction

Nature Vs Nurture in Relation to Drug Addiction

• Categories: Drug Abuse Drug Addiction Nature Versus Nurture

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Published: Feb 8, 2022

Words: 1762 | Pages: 4 | 9 min read

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Introduction, topic analysis.

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• Braun, K., & Champagne, F. A. (2014). Paternal Influences on Offspring Development: Behavioural and Epigenetic Pathways. Journal of Neuroendocrinology, 26(10), 697–706. https://doi.org/10.1111/jne.12174
• Crabbe, J. C. (2002). Genetic Contributions to Addiction. Annual Review of Psychology, 53(1), 435. https://doi.org/10.1146/annurev.psych.53.100901.135142
• Larkin, M., Wood, R. T. A., & Griffiths, M. D. (2006). Towards addiction as a relationship. Addiction Research & Theory, 14(3), 207–215. https://doi.org/10.1080/16066350500151747
• Lyvers, M. (1998). Drug addiction as a physical disease: The role of physical dependence and other chronic drug-induced neurophysiological changes in compulsive drug self-administration. Experimental and Clinical Psychopharmacology, 6(1), 107–125. https://doi.org/10.1037/1064-1297.6.1.107
• Sadava, S. W., & Forsyth, R. (1976). Drug Use and a Social Psychology of Change. British Journal of Addiction (to Alcohol & Other Drugs), 71(4), 335–342. https://doi.org/10.1111/j.1360-0443.1976.tb00104.x
• Volkow, N. D., & Ting-Kai Li. (2004). Science and Society: Drug addiction: the neurobiology of behaviour gone awry. Nature Reviews Neuroscience, 5(12), 963–970. https://doi.org/10.1038/nrn1539
• Winger, G., Woods, J. H., Galuska, C. M., & Wade-Galuska, T. (2005). Behavioural perspectives on the neuroscience of drug addiction. Journal of the experimental analysis of behaviour, 84(3), 667–681. doi:10.1901/jeab.2005.101-04

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80 Nature vs Nurture Essay Topics & Examples

Have some suggestions and questions about nature vs nurture? On this page, find research and essay topics to explore a particular aspect of the discussion.

📑 Aspects to Cover in a Nature vs Nurture Essay

🏆 best nature vs nurture essay topics & essay examples, 📌 most interesting nurture vs nature topics to write about, 👍 good nature vs nurture topics, ❓ questions about nature vs nurture.

What affects human development: nature or nurture? Are gender roles and differences come naturally, or does society impose them? What can be argued about the personalities of identical twins? Explore any of the issues with us! Our IvyPnada team has prepared nurture vs nature topics to write about. Check essay examples via the links as well.

At first glance, a nature vs nurture essay seems to be easy. However, a limited view of the subject matter may cost you marks, which is why it is crucial to offer a well-rounded account of the debate. Here are some of the aspects that you might want to include in your essay on nature vs nurture.

• The importance of the topic. The debate on what influences one’s personality, intelligence, and character is among the most prominent ones in psychology and other social sciences. Your task is to reflect this and to attempt to justify why the debate is so important. What could be done if it were resolved one day? How does the dispute affect other subject fields and topics in psychology? How would the resolution help the study of psychology and human behavior to move forward? Would it help to prove certain theories or refute the others, and what would be the effect on professional practice?
• The origins of the debate. While you explore the first aspect, you might stumble upon the history of the nature vs nurture debate. Covering this theme in your essay could also earn you some extra marks. Merely summarizing historical facts is not enough, though, because your tutor is probably aware of them already. Instead, you should focus on why the debate started. Were there any developments in psychology that prompted it?
• Prominent views. It is hard to omit the opinions expressed by famous scholars while writing an essay on this subject. John Locke, John B. Watson, Calvin Hall, and other authors had all shared ideas on the issue. If you need more names, try searching sample essays on nature and nurture online since most of them point out the key names. This might also help you to identify possible nature vs nurture essay titles.
• Results of research studies. Research evidence is among the key nature vs nurture essay topics because there were many attempts to prove one or the other view. Examples of such studies may be cited in your textbook, so it should be the first point of your research. Your school’s library and Google Scholar might also give you more information. If you find any sources online, make sure that they are of academic quality, or you might lose marks.
• Your personal experience and thoughts. Because the controversy is so prominent, nearly all people who study psychology or social studies have an opinion on it. If the instructions don’t prevent you from doing this, you should share your thoughts on the debate between nature and nurture. Support your opinion with credible research evidence and link it to the work of other scholars. If you believe that the environment is more important than genes, why is that? What other theorists supported this view, and why did they? Your opinion, supported by relevant facts and views, may become an excellent nature vs nurture essay thesis.
• Suggestions for further research. Try to think about what could be done to resolve the debate once and for all. What are the main gaps in studies on nature vs nurture and how could they be addressed by scholars?

Covering all of the themes above will help you to produce an outstanding essay. Make sure to check our website for a nature vs nurture essay prompt, titles, and other useful materials!

• Nature vs. Nurture In most cases, nature determines the physical characteristics which in effect influence the behavior of an individual. These are traits which largely determined by the socio-cultural environmental factors or the way the individuals are socialized […]
• Human Development: Nature or Nurture? With studies and theories carried out to examine the impact of nature on the personal development and personality traits, heredity is an important factor in the development.
• As Nature Made Him: Summary and Analysis As aforementioned, the author of this book provides useful analysis of this aspect of personality. One of the greatest questions that readers get answer from this book is the question of nature vs.nurture in sexuality […]
• Nature vs. Nurture: “In Cold Blood” by Truman Capote Thus, by contrasting Dick’s nurturing in love and affection and the conditions of his blissful childhood and adolescence with the details of a horrible crime committed by him and his attitude to it, the author […]
• Physical and Mental Wellbeing: Nature Versus Nurture In conclusion, the debates on nature versus nurture reveal that both innate health conditions and external factors shape the outcomes for physical and mental wellbeing of an individual.
• Nature Versus Nurture and Learning Among Children Of much concern among modern researchers is the determination of the degree of influence of nature and nurture on the development of a child and the provision of learning experiences.
• Violent Behavior: Nature vs. Nurture Considering this circumstance, the shifts in one’s attitudes are likely to be ascribed to the modifications in conditions, which can be reported by families with children.
• “Nature” Versus “Nurture”: Effects on Child Development Consequently, a child’s behavior cannot be viewed as solely attributable to the genetic composition of the parents and the hereditary characteristics.
• Nature vs. Nurture: New Science Stirs Debate How Behavior Is Shaped A prime example of this nature of debates is the debate on whether nature or nurture has a greater bearing on the development of the diverse individual behavioral differences that exist.
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