The dopamine transporter gene, a spectrum of most common risky behaviors, and the legal status of the behaviors

Prominent genetic variants and epigenetic changes in post-traumatic stress disorder among combat veterans

Post-traumatic stress disorder (PTSD) is one of the most widespread and disabling psychiatric disorders among combat veterans. Substantial interindividual variability in susceptibility to PTSD suggests the presence of different risk factors for this disorder. Twin and family studies confirm genetic factors as important risk factors for PTSD. In addition to genetic factors, epigenetic factors, especially DNA methylation, can be considered as a potential mechanism in changing the risk of PTSD. So far, many genetic and epigenetic association studies have been conducted in relation to PTSD. In genetic studies, many single nucleotide polymorphisms have been identified as PTSD risk factors. Meanwhile, the variations in catecholamines-related genes, serotonin transporter and receptors, brain-derived neurotrophic factor, inflammatory factors, and apolipoprotein E are the most prominent candidates. CpG methylation in the upstream regions of many genes is also considered a PTSD risk factor. Accurate identification of genetic and epigenetic changes associated with PTSD can lead to the presentation of suitable biomarkers for susceptible individuals to this disorder. This study aimed to delineate prominent genetic variations and epigenetic changes associated with post-traumatic stress disorder in military veterans who have experienced combat, focusing on genetic and epigenetic association studies.

Association of Dopamine Transporter Gene (DAT1) 40 bp 3′ UTR VNTR Polymorphism (rs28363170) and Cannabis Use Disorder

Introduction:

Cannabis remains the most widely used illicit drug among Nigerians, often associated with psychiatric disorders. Since genetic predisposition has been implicated in substance use disorders, we, therefore, aimed at finding out the relationship between dopamine transporter gene (DAT1) polymorphism and cannabis use disorder.

Methods:

We recruited 104 patients from a tertiary psychiatric facility in Lagos, Nigeria, who were diagnosed with cannabis use disorder according to ICD-10 and 96 non-smokers as a comparative group. The smokers were screened with Cannabis Use Disorder Identification Test (CUDIT), and cannabis dependence was assessed with the Severity of Dependence Scale (SDS). Genotyping was carried out for the 40 bp 3′ UTR VNTR of the DAT1 (rs28363170).

Results:

The frequencies of 9R/9R, 9R/10R, 10R/10R among non-smokers and smokers were 14 (14.3%), 25 (26.2%), 57 (59.5%) and 17 (16.3%), 54 (51.9%), 33 (31.7%) respectively. The genotype distribution was in Hardy Weinberg equilibrium (HWE) only in the smokers’ population (χ² = 1.896, P = .166). Individuals with the 10R allele were almost twice as likely as the 9R carriers to smoke cannabis (OR = 1.915, 95% CI: 1.225-2.995). However, this polymorphism was not associated with the quantity of cannabis smoked, age at onset of smoking, CUDIT, and SDS scores.

Conclusion:

The DAT VNTR polymorphism was associated with cannabis smoking but not cannabis use disorder.

FOXN3 and GDNF Polymorphisms as Common Genetic Factors of Substance Use and Addictive Behaviors

Epidemiological and phenomenological studies suggest shared underpinnings between multiple addictive behaviors. The present genetic association study was conducted as part of the Psychological and Genetic Factors of Addictions study (n = 3003) and aimed to investigate genetic overlaps between different substance use, addictive, and other compulsive behaviors. Association analyses targeted 32 single-nucleotide polymorphisms, potentially addictive substances (alcohol, tobacco, cannabis, and other drugs), and potentially addictive or compulsive behaviors (internet use, gaming, social networking site use, gambling, exercise, hair-pulling, and eating). Analyses revealed 29 nominally significant associations, from which, nine survived an FDRbl correction. Four associations were observed between FOXN3 rs759364 and potentially addictive behaviors: rs759364 showed an association with the frequency of alcohol consumption and mean scores of scales assessing internet addiction, gaming disorder, and exercise addiction. Significant associations were found between GDNF rs1549250, rs2973033, CNR1 rs806380, DRD2/ANKK1 rs1800497 variants, and the “lifetime other drugs” variable. These suggested that genetic factors may contribute similarly to specific substance use and addictive behaviors. Specifically, FOXN3 rs759364 and GDNF rs1549250 and rs2973033 may constitute genetic risk factors for multiple addictive behaviors. Due to limitations (e.g., convenience sampling, lack of structured scales for substance use), further studies are needed. Functional correlates and mechanisms underlying these relationships should also be investigated.

Efficacy of intervention at traffic schools reducing impulsive action, and association with candidate gene variants

OBJECTIVE

Road traffic injuries are the leading cause of death among young people. Recognition of the contribution of impulsive behaviour may help novice drivers to behave more safely. Previously a brief intervention focusing on impulsive traffic behaviour conducted by psychologists in driving schools had been effective. The aim of this study was an independent re-evaluation of the effect of the intervention, as conducted by driving school teachers, and assessment of the potential associations with candidate genotypes.

METHODS

Driving school students (mean age 22.5, SD=7.9) were divided into intervention (n=704) and control (n=737) groups. Driving school teachers were trained to administer the intervention which consisted of a lecture and group work (1.5 h in total) on impulsivity. Traffic offences and crashes were monitored during 3 years, using police and traffic insurance fund databases. Functional polymorphisms of the dopamine transporter (DAT) and serotonin transporter genes (DAT1 VNTR and 5-HTTLPR) were assessed.

RESULTS

The intervention significantly lowered general traffic risk and prevalence of traffic accidents. DAT1 VNTR 9R carriers, particularly males, had higher general traffic risk in the whole sample. Female 5-HTTLPR s' allele carriers of the intervention group had the lowest general traffic risk. Intervention was most effective in female DAT1 VNTR 10R/10R homozygotes.

CONCLUSIONS

Brief impulsivity-centred intervention appears as a promising strategy for preventing risk-taking behaviour in novice drivers and can be fully integrated to driving school curriculum.

Pharmacogenetic role of dopamine transporter (SLC6A3) variation on response to disulfiram treatment for cocaine addiction

BACKGROUND AND OBJECTIVES

Disulfiram has been beneficial in treating cocaine addiction in several studies. Patients with two SLC6A3 (DAT1) rs28363170 10-repeat alleles who have with genetically high dopamine transporter (DAT) levels may benefit from increased dopamine levels resulting from disulfiram treatment.

METHODS

After stabilization for 2 weeks on methadone, 70 cocaine and opioid codependent patients were randomized into disulfiram and placebo groups for 12 weeks of treatment. We genotyped the SLC6A3 (DAT1) 40 bp 3'-untranslated region variable number tandem repeat variant and evaluated its role in moderating disulfiram efficacy for cocaine dependence.

RESULTS

Among the 10,10-repeat genotype group, cocaine-positive urines dropped from 78% to 48% and from 80% to 75% among the 9-repeat carrier group in the disulfiram group (P = 0.0001, with an effect size of 0.09). No difference was observed in cocaine-positive urines in the placebo group between the 10,10-repeat genotype and the 9-allele carrier patients.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

We found that patients with genetically higher DAT levels had better treatment outcomes with disulfiram pharmacotherapy of cocaine dependence than those with lower DAT levels. (Am J Addict 2019;28:311-317).

Genetic and Environmental Risk Factors for Cannabis Use: Preliminary Results for the Role of Parental Care Perception

BACKGROUND

Vulnerability to cannabis use (CU) initiation and problematic use have been shown to be affected by both genetic and environmental factors, with still inconclusive and uncertain evidence.

OBJECTIVE

Aim of the present study was to investigate the possible interplay between gene polymorphisms and psychosocial conditions in CU susceptibility.

METHODS

Ninety-two cannabis users and ninety-three controls have been included in the study. Exclusion criteria were serious mental health disorders and severe somatic disorders, use of other drugs and alcohol abuse; control subjects were not screened to remove Reward Deficiency Syndrome (RDS) behaviors. A candidate gene association study was performed, including variants related to dopaminergic and endocannabinoids pathways. Adverse childhood experiences and quality of parental care have been retrospectively explored utilizing ACES (Adverse Children Experience Scale), CECA-q (Child Experience of Care and Abuse Questionnaire), PBI (Parental Bonding Instrument).

RESULTS

Our findings evidenced a significant association between rs1800497 Taq1A of ANKK1 gene and CU. Parental care was found to be protective factor, with emotional and physical neglect specifically influencing CU. Gender also played a role in CU, with males smoking more than females. However, when tested together genotypes and psychosocial variables, the significance of observed genetic differences disappeared.

CONCLUSIONS

Our results confirm a significant role of Taq1A polymorphism in CU vulnerability. A primary role of environmental factors in mediating genetic risk has been highlighted: parental care could be considered the main target to design early prevention programs and strategies.

Activation of RHO-1 in cholinergic motor neurons competes with dopamine signalling to control locomotion

The small GTPase RhoA plays a crucial role in the regulation of neuronal signalling to generate behaviour. In the developing nervous system RhoA is known to regulate the actin cytoskeleton, however the effectors of RhoA-signalling in adult neurons remain largely unidentified. We have previously shown that activation of the RhoA ortholog (RHO-1) in C. elegans cholinergic motor neurons triggers hyperactivity of these neurons and loopy locomotion with exaggerated body bends. This is achieved in part through increased diacylglycerol (DAG) levels and the recruitment of the synaptic vesicle protein UNC-13 to synaptic release sites, however other pathways remain to be identified. Dopamine, which is negatively regulated by the dopamine re-uptake transporter (DAT), has a central role in modulating locomotion in both humans and C. elegans. In this study we identify a new pathway in which RHO-1 regulates locomotory behaviour by repressing dopamine signalling, via DAT-1, linking these two pathways together. We observed an upregulation of dat-1 expression when RHO-1 is activated and show that loss of DAT-1 inhibits the loopy locomotion phenotype caused by RHO-1 activation. Reducing dopamine signalling in dat-1 mutants through mutations in genes involved in dopamine synthesis or in the dopamine receptor DOP-1 restores the ability of RHO-1 to trigger loopy locomotion in dat-1 mutants. Taken together, we show that negative regulation of dopamine signalling via DAT-1 is necessary for the neuronal RHO-1 pathway to regulate locomotion.

Biological and Behavioral Mechanisms of Identity Pathology Development: An Integrative Review

Although identity disturbance is a transdiagnostic mental health problem, modern explanatory models for its emergence are limited. To date, the social, developmental, clinical, and neuropsychological literatures exploring identity processes are also largely disconnected. Existing theories have laid the foundation for understanding important components of identity pathology, yet many overlook biological, behavioral, and interactive processes by which these difficulties may emerge. In this integrative review, we explore how broad transdiagnostic vulnerabilities for psychopathology and more specific risky behavioral processes may reciprocally interact and be refined over time into an identity disturbance profile. Our primary purpose is to review behavioral and biosocial theories and derive a testable conceptual framework for how identity disturbance emerges over the course of development. We aim to describe and integrate several disparate lines of theory and research in order to illuminate potential etiological pathways to identity pathology.

Waist circumference, body mass index, and employment outcomes

Body mass index (BMI) is an imperfect measure of body fat. Recent studies provide evidence in favor of replacing BMI with waist circumference (WC). Hence, I investigated whether or not the association between fat mass and employment status vary by anthropometric measures. I used 15 rounds of the Health Survey for England (1998-2013), which has measures of employment status in addition to measured height, weight, and WC. WC and BMI were entered as continuous variables and obesity as binary variables defined using both WC and BMI. I used multivariate models controlling for a set of covariates. The association of WC with employment was of greater magnitude than the association between BMI and employment. I reran the analysis using conventional instrumental variables methods. The IV models showed significant impacts of obesity on employment; however, they were not more pronounced when WC was used to measure obesity, compared to BMI. This means that, in the IV models, the impact of fat mass on employment did not depend on the measure of fat mass.

Externalizing Problem Behavior in Adolescence: Parenting Interacting With DAT1 and DRD4 Genes

This study extends previous gene-by-environment (G × E) research through design and methodological advances and examines alternative hypotheses of diathesis stress, vantage sensitivity, and differential susceptibility. In a sample of 984 adolescents and their parents, we examined whether effects of parental support, proactive, punitive, harsh punitive, and psychological control on externalizing problem behavior are moderated by adolescents' genotype for the dopamine transporter (DAT1) or receptor D4 (DRD4) gene. Results provided evidence for main effects of parenting behavior and DRD4, and multiple interaction effects of which one survived Bonferroni correction. Adolescents carrying a long DRD4 variant were more susceptible to the effects of parental proactive control on aggression, for better and for worse. Critical considerations were made regarding the complexity of G × E research.

Environmental risks outweigh dopaminergic genetic risks for alcohol use and abuse from adolescence through early adulthood

BACKGROUND

Alcohol use is a primary public health concern, particularly among adolescents and young adults. Based on the rapidly growing field of gene-environment models, this study assessed the combined role of environmental and dopamine-related genetic correlates of early alcohol use and abuse.

METHODS

Multilevel growth models assessed trajectories of alcohol use and intoxication and ordered logistic regressions assessed alcohol use disorder among a sample of 12,437 youth from the nationally representative Add Health study who were followed from mid-adolescence through early adulthood.

RESULTS

Endogenous and exogenous stressful life events and social norms supportive of alcohol use from parents and peers were significant predictors of alcohol use, intoxication, and alcohol use disorder, with consistent patterns across males and females. In contrast, a dopamine-system genetic risk score (GRS) was not associated with alcohol use trajectories nor alcohol use disorder in early adulthood, although weak connections emerged between the GRS and growth trajectories of intoxication, indicating that higher GRS predicted more frequent episodes of intoxication during the transition to adulthood but not during adolescence or later 20s. No evidence of gene-environment interactions emerged.

CONCLUSIONS

Results extend a substantial body of prior research primarily assessing single genetic polymorphisms in the dopamine system, suggesting that dopaminergic GRSs may be associated with more problematic alcohol behaviors at some developmental periods, but further, that social norms and stressful life experiences are more consistent correlates of early and problematic alcohol use among youth. These environmental factors present potential targets for research manipulating contexts to identify causal pathways.

The Impact of Childhood Obesity on Health and Health Service Use

OBJECTIVE

To test the impact of obesity on health and health care use in children, by the use of various methods to account for reverse causality and omitted variables.

DATA SOURCES/STUDY SETTING

Fifteen rounds of the Health Survey for England (1998-2013), which is representative of children and adolescents in England.

STUDY DESIGN

We use three methods to account for reverse causality and omitted variables in the relationship between BMI and health/health service use: regression with individual, parent, and household control variables; sibling fixed effects; and instrumental variables based on genetic variation in weight.

DATA COLLECTION/EXTRACTION METHODS

We include all children and adolescents aged 4-18 years old.

PRINCIPAL FINDINGS

We find that obesity has a statistically significant and negative impact on self-rated health and a positive impact on health service use in girls, boys, younger children (aged 4-12), and adolescents (aged 13-18). The findings are comparable in each model in both boys and girls.

CONCLUSIONS

Using econometric methods, we have mitigated several confounding factors affecting the impact of obesity in childhood on health and health service use. Our findings suggest that obesity has severe consequences for health and health service use even among children.

A genetic marker of risk in HIV-infected individuals with a history of hazardous drinking

Impulsivity and sensation seeking have been linked to hazardous drinking, increased sexual risk behaviors, and lower treatment adherence among persons living with HIV (PLH). The dopamine active transporter1 (DAT1or SLC6A3) gene has been linked to impulsivity and sensation seeking in several populations but has not been investigated among populations of PLH. This study used data from 201 PLH who report a recent history of heavy episodic drinking. Results indicate that DAT1*10R vs DAT1*9R genotype was related to higher propensity for risk taking (standardized difference score (d) = 0.30 [95% CI: 0.02;0.59]), more hazardous drinking (d = 0.35 [0.05;0.64]), and more condomless sex (rate ratio (RR)= 2.35[1.94; 2.85]), but were counter-intuitively associated with fewer sexual partners (RR = 0.65[0.43;0.91]) and possibly better treatment adherence (d = 0.32 [-0.01;0.65]). Results are consistent with the suggested associations between DAT1 and risk-taking behavior. The counter-intuitive finding for partner selection and treatment adherence may be evidence of additional factors that place PLH at risk for engaging in hazardous drinking as well as relationship difficulties and problems with treatment adherence (e.g., depressive symptoms, avoidant coping, trauma history). Caution is required when using a single gene variant as a marker of complex behaviors and these findings need to be replicated using larger samples and additional variants.

Socio-Genomics and Structural Competency

Adverse developmental exposures and pathologies of the social environment make vastly greater contributions to the leading health burdens in society than currently known genotypic information. Yet, while patients now commonly bring information on single alleles to the attention of their healthcare team, the former conditions are only rarely considered with respect to future health outcomes. This manuscript aims to integrate social environmental influences in genetic predictive models of disease risk. Healthcare providers must be educated to better understand genetic risks for complex diseases and the specific health consequences of societal adversities, to facilitate patient education, disease prevention, and the optimal care in order to achieve positive health outcomes for those with early trauma or other social disadvantage.

Transactional Links Between Teacher-Student Relationships and Adolescent Rule-Breaking Behavior and Behavioral School Engagement: Moderating Role of a Dopaminergic Genetic Profile Score

Throughout adolescence, there is an increase in rule-breaking behavior and a decrease in behavioral school engagement. The role of teacher-student relationship quality in the development of these adjustment problems remains understudied. This study examined how adolescent-reported teacher-student affiliation and dissatisfaction and parent-reported rule-breaking behavior and behavioral engagement impact one another throughout adolescence. In addition, we examined the moderating effect of genes by means of a Biologically Informed Multilocus genetic Profile Score (BIMPS), a composite score reflecting the cumulative effect of multiple dopaminergic genes, with a higher score indicating higher dopamine signaling in the adolescent brain. We used three-year longitudinal data from 1111 adolescents (51 % boys; M age = 13.79), and their parents. Cross-lagged analyses revealed a transactional process in which adolescents who display more rule-breaking behavior and less behavioral engagement experienced increased subsequent dissatisfaction with their teachers, which in turn further increased their adjustment problems. Also, adolescents with more adjustment problems experienced decreased subsequent affiliation with their teachers. The other way around, adolescents' behavioral engagement also benefitted from positive relationships with teachers. Multi-group analyses revealed genetic moderation for behavioral engagement, but not for rule-breaking. Specifically, adolescents who had a BIMPS score coding for moderate levels of dopamine signaling (instead of high or low signaling) were most affected in their behavioral engagement when they experienced dissatisfaction with their teachers. Our study findings may guide schools in implementing interventions to create a supportive class and school environment including positive, supportive teacher-student relationships and indicate that providing a such a supportive school environment is important for all adolescents.

Teacher-student relationships and adolescent behavioral engagement and rule-breaking behavior: The moderating role of dopaminergic genes

This study examined whether the dopamine transporter DAT1 and the dopamine receptor DRD4 genes moderate the effect of student-reported teacher-student relationship affiliation or dissatisfaction on parent-reported adolescent rule-breaking behavior and behavioral engagement. The sample included 1053 adolescents (51% boys, Mage=13.79) from grades 7 to 9. Regression analyses were conducted using Mplus while controlling for multiple testing and nested data. Adolescents who experienced stronger affiliation with their teachers were more engaged in school, whereas greater dissatisfaction predicted more rule-breaking behavior. In addition, a significant gene-environment interaction was found for both genes examined. The link between low teacher-student affiliation and low engagement was more pronounced for DAT1-10R homozygotes. The link between high teacher-student dissatisfaction and more rule-breaking was stronger for DRD4 non-long carriers. Implications for understanding the role of teacher-student relationships in adolescence and suggestions for future research are outlined.

Sibling genes as environment: Sibling dopamine genotypes and adolescent health support frequency dependent selection

While research consistently suggests siblings matter for individual outcomes, it remains unclear why. At the same time, studies of genetic effects on health typically correlate variants of a gene with the average level of behavioral or health measures, ignoring more complicated genetic dynamics. Using National Longitudinal Study of Adolescent Health data, we investigate whether sibling genes moderate individual genetic expression. We compare twin variation in health-related absences and self-rated health by genetic differences at three locations related to dopamine regulation and transport to test sibship-level cross-person gene-gene interactions. Results suggest effects of variation at these genetic locations are moderated by sibling genes. Although the mechanism remains unclear, this evidence is consistent with frequency dependent selection and suggests much genetic research may violate the stable unit treatment value assumption.

Mesocorticolimbic dopamine functioning in primary psychopathy: A source of within-group heterogeneity

Despite similar emotional deficiencies, primary psychopathic individuals can be situated on a continuum that spans from controlled to disinhibited. The constructs on which primary psychopaths are found to diverge, such as self-control, cognitive flexibility, and executive functioning, are crucially regulated by dopamine (DA). As such, the goal of this review is to examine which specific alterations in the meso-cortico-limbic DA system and corresponding genes (e.g., TH, DAT, COMT, DRD2, DRD4) might bias development towards a more controlled or disinhibited expression of primary psychopathy. Based on empirical data, it is argued that primary psychopathy is generally related to a higher tonic and population activity of striatal DA neurons and lower levels of D2-type DA receptors in meso-cortico-limbic projections, which may boost motivational drive towards incentive-laden goals, dampen punishment sensitivity, and increase future reward-expectancy. However, increasingly higher levels of DA activity in the striatum (moderate versus pathological elevations), lower levels of DA functionality in the prefrontal cortex, and higher D1-to-D2-type receptor ratios in meso-cortico-limbic projections may lead to increasingly disinhibited and impetuous phenotypes of primary psychopathy. Finally, in order to provide a more coherent view on etiological mechanisms, we discuss interactions between DA and serotonin that are relevant for primary psychopathy.

Genes in the dopaminergic system and delinquent behaviors across the life course: the role of social controls and risks

This paper examines the interaction between social control and social risk mechanisms and genes within the dopaminergic system (DAT1 and DRD2) as related to serious and violent forms of delinquent behavior among adolescents and young adults. We use nine waves of data from the National Youth Survey Family Study to examine the relevance of protective or risky social factors at four social levels including school, neighborhood, friends, and family within the gene-environment interaction framework. We extend previous work in this area by providing a testable typology of gene-environment interactions derived from current theories in this area. We find consistent evidence that the associations between putatively risky genotypes and delinquent behavior are suppressed within protective social environments. We also provide some evidence that supports the differential susceptibility hypothesis for these outcomes. Our findings largely confirm the conclusions of previous work and continue to highlight the critical role of the social environment within candidate gene studies of complex behaviors.

The role of gene-gene interaction in the prediction of criminal behavior

A host of research has examined the possibility that environmental risk factors might condition the influence of genes on various outcomes. Less research, however, has been aimed at exploring the possibility that genetic factors might interact to impact the emergence of human traits. Even fewer studies exist examining the interaction of genes in the prediction of behavioral outcomes. The current study expands this body of research by testing the interaction between genes involved in neural transmission. Our findings suggest that certain dopamine genes interact to increase the odds of criminogenic outcomes in a national sample of Americans.

Exploring whether genetic differences between siblings explain sibling differences in criminal justice outcomes

Research has revealed that despite many similarities, siblings raised within the same household have also been found to be markedly different from one another. Behavioral differences between siblings have been primarily attributed to differential exposure to a wide variety of environmental influences. The potential role that between-sibling genetic differences play in the development of behavioral differences has been overlooked in the extant literature. The current study examines the association between differences in three dopaminergic polymorphisms (DAT1, DRD2, and DRD4) and differences in arrest, incarceration, and multiple arrests between siblings. Between-sibling difference scores were estimated for each examined polymorphism and each criminal justice outcome measure (along with all controls). Ordinary least squares (OLS) regression models were estimated to examine the potential association between genetic differences between siblings and differences in experiences within the criminal justice system. Models were estimated for the full sample and then for the same-sex male and female subsamples separately. The results provide preliminary evidence that between-sibling differences in some of the examined dopaminergic polymorphisms are associated with differences in contact with the criminal justice system. Findings are discussed in more detail and suggestions for future research are also provided.

The challenge of causal inference in gene-environment interaction research: leveraging research designs from the social sciences

The integration of genetics and the social sciences will lead to a more complex understanding of the articulation between social and biological processes, although the empirical difficulties inherent in this integration are large. One key challenge is the implications of moving "outside the lab" and away from the experimental tools available for research with model organisms. Social science research methods used to examine human behavior in nonexperimental, real-world settings to date have not been fully taken advantage of during this disciplinary integration, especially in the form of gene-environment interaction research. This article outlines and provides examples of several prominent research designs that should be used in gene-environment research and highlights a key benefit to geneticists of working with social scientists.

Social, behavioral, and genetic linkages from adolescence into adulthood

The influence of genetic factors on health and behavior is conditioned by social, cultural, institutional, and physical environments in which individuals live, work, and play. We encourage studies supporting multilevel integrative approaches to understanding these contributions to health, and describe the Add Health study as an exemplar. Add Health is a large sample of US adolescents in grades 7 to 12 in 1994-1995 followed into adulthood with 4 in-home interviews and biomarker collections, including DNA. In addition to sampling multiple environments and measuring diverse social and health behavior, Add Health features a fully articulated behavioral genetic sample (3000 pairs) and ongoing genotyping of 12,000 archived samples. We illustrate approaches to understanding health through investigation of the interplay among biological, psychosocial, and physical, contextual, or cultural experiences.

Genetic sensitivity to peer behaviors: 5HTTLPR, smoking, and alcohol consumption

We investigate whether the serotonin transporter-linked polymorphic region (5HTTLPR), a gene associated with environmental sensitivity, moderates the association between smoking and drinking patterns at adolescents' schools and their corresponding risk for smoking and drinking themselves. Drawing on the school-based design of the National Longitudinal Study of Adolescent Health in conjunction with molecular genetic data for roughly 15,000 respondents (including over 2,000 sibling pairs), we show that adolescents smoke more cigarettes and consume more alcohol when attending schools with elevated rates of tobacco and alcohol use. More important, an individual's susceptibility to school-level patterns of smoking or drinking is conditional on the number of short alleles he or she has in 5HTTLPR. Overall, the findings demonstrate the utility of the differential susceptibility framework for medical sociology by suggesting that health behaviors reflect interactions between genetic factors and the prevalence of these behaviors in a person's context.

The National Longitudinal Study of Adolescent Health (Add Health) sibling pairs data

This article describes the design and phenotype and genotype data available for sibling pairs with varying genetic relatedness in the National Longitudinal Study of Adolescent Health (Add Health). Add Health is a nationally representative longitudinal study of over 20,000 adolescents in the United States in 1994-1995 who have been followed for 15 years into adulthood. The Add Health design included oversamples of more than 3,000 pairs of individuals with varying genetic resemblance, ranging from monozygotic twins, dizygotic twins, full siblings, half siblings, and unrelated siblings who were raised in the same household. Add Health sibling pairs are therefore nationally representative and followed longitudinally from early adolescence into adulthood with four in-home interviews during the period 1994-2009. Add Health has collected rich longitudinal social, behavioral, environmental, and biological data, as well as buccal cell DNA from all sample members, including sibling pairs. Add Health has an enlightened dissemination policy and to date has released phenotype and genotype data to more than 10,000 researchers in the scientific community.

DAT1 polymorphism is associated with risk taking in the Balloon Analogue Risk Task (BART)

Twin-studies suggest that a significant portion of individual differences in the propensity to take risks resides in people’s genetic make-up and there is evidence that variability in dopaminergic systems relates to individual differences in risky choice. We examined the link between risk taking in a risk taking task (the Balloon Analogue Risk Task, BART) and a variable number tandem repeat (VNTR) polymorphism in the 3′UTR of the dopamine transporter gene (SLC6A3/DAT1). Behavior in BART is known to be associated with activity in striatal reward-processing regions, and DAT1 is assumed to modulate striatal dopamine levels. We find that carriers of DAT1 alleles, which presumably result in lower striatal dopamine availability, showed more risk taking, relative to carriers of the alleles associated with higher striatal dopamine availability. Our analyses suggest that the mechanism underlying this association is diminished sensitivity to rewards among those who take more risks. Overall, our results support the notion that a behavioral genetic approach can be helpful in uncovering the basis of individual differences in risk taking.

Genetically determined dopamine availability predicts disposition for depression

Although prominent personality theories postulate orthogonality between traits of positive emotionality (PEM) and negative emotionality (NEM), empirical evidence often demonstrates the opposite indicating a negative relationship. Therefore, it is not surprising that dopaminergic (DA) gene loci have been related to traits of positive and of NEM. The present genetic association study investigates the influence of two functional DA gene polymorphisms on Sadness as defined by the Affective Neuroscience Personality Scales (ANPS) in healthy Caucasians (n = 1041). We observed a significant interaction effect between the 10-repeat (10R) allele of the dopamine transporter (DAT1) gene and the methionine (Met) allele of the catechol-O-methyltransferase (COMT) Val158Met polymorphism (F((1,1018)) = 11.11; P < 0.001). Carriers of the 9R/9R and the Val/Val genotype showed dramatically reduced Sadness scores in comparison to the other three genotype configurations. Both the 9R/9R and the Val/Val genotypes characterized by reduced transporter density and high dopamine catabolism, respectively, have been separately related to personality traits of PEM and externalizing behavior in the past. The present findings indicate that gene variations of the DA system previously associated with PEM are at the same time protective against high NEM and can therefore constitute a resilience factor against depression.