The relationship between risk-taking propensity and the COMT Val(158)Met polymorphism among early adolescents as a function of sex

Polygenic contributions to performance on the Balloon Analogue Risk Task

Risky decision-making is a common, heritable endophenotype seen across many psychiatric disorders. Its underlying genetic architecture is incompletely explored. We examined behavior in the Balloon Analogue Risk Task (BART), which tests risky decision-making, in two independent samples of European ancestry. One sample (n = 1138) comprised healthy participants and some psychiatric patients (53 schizophrenia, 42 bipolar disorder, 47 ADHD); the other (n = 911) excluded for recent treatment of various psychiatric disorders but not ADHD. Participants provided DNA and performed the BART, indexed by mean adjusted pumps. We constructed a polygenic risk score (PRS) for discovery in each dataset and tested it in the other as replication. Subsequently, a genome-wide MEGA-analysis, combining both samples, tested genetic correlation with risk-taking self-report in the UK Biobank sample and psychiatric phenotypes characterized by risk-taking (ADHD, Bipolar Disorder, Alcohol Use Disorder, prior cannabis use) in the Psychiatric Genomics Consortium. The PRS for BART performance in one dataset predicted task performance in the replication sample (r = 0.13, p = 0.000012, pFDR = 0.000052), as did the reciprocal analysis (r = 0.09, p = 0.0083, pFDR=0.04). Excluding participants with psychiatric diagnoses produced similar results. The MEGA-GWAS identified a single SNP (rs12023073; p = 3.24 × 10-8) near IGSF21, a protein involved in inhibitory brain synapses; replication samples are needed to validate this result. A PRS for self-reported cannabis use (p = 0.00047, pFDR = 0.0053), but not self-reported risk-taking or psychiatric disorder status, predicted behavior on the BART in our MEGA-GWAS sample. The findings reveal polygenic architecture of risky decision-making as measured by the BART and highlight its overlap with cannabis use.

The Genetics of Risk Aversion: A Systematic Review

Risk and loss aversion are phenomena with an important influence on decision-making, especially in economic contexts. At present, it remains unclear whether both are related, as well as whether they could have an emotional origin. The objective of this review, following the PRISMA statements, is to find consistencies in the genetic bases of risk and loss aversion with the aim of understanding their nature and shedding light on the above issues. A total of 23 empirical research met the inclusion criteria and were included from PubMed and ScienceDirect. All of them reported genetic measures from human samples and studied risk and loss aversion within an economic framework. The results for risk aversion, although with many limitations, attributed mainly to their heterogeneity and the lack of control in the studies, point to the implication of multiple polymorphisms related to the regulation of the serotonergic and dopaminergic pathways. In general, studies found the highest levels of risk aversion were associated with alleles that are linked to lower (higher) sensitivity or levels of dopamine (serotonin). For loss aversion, the scarcity of results prevents us from drawing clear conclusions, although the limited evidence seems to point in the same direction as for risk aversion. Therefore, it seems that risk aversion could have a stable genetical base which, in turn, is closely linked to emotions, but more research is needed to answer whether this phenomenon is related to loss aversion, as well as if the latter could also have an emotional origin. We also provide recommendations for future studies on genetics and economic behavior.

Developmental differences in description-based versus experience-based decision making under risk in children

The willingness to take a risk is shaped by temperaments and cognitive abilities, both of which develop rapidly during childhood. In the adult developmental literature, a distinction is drawn between description-based tasks, which provide explicit choice-reward information, and experience-based tasks, which require decisions from past experience, each emphasizing different cognitive demands. Although developmental trends have been investigated for both types of decisions, few studies have compared description-based and experience-based decision making in the same sample of children. In the current study, children (N = 112; 5-9 years of age) completed both description-based and experience-based decision tasks tailored for use with young children. Child temperament was reported by the children's primary teacher. Behavioral measures suggested that the willingness to take a risk in a description-based task increased with age, whereas it decreased in an experience-based task. However, computational modeling alongside further inspection of the behavioral data suggested that these opposite developmental trends across the two types of tasks both were associated with related capacities: older (vs. younger) children's higher sensitivity to experienced losses and higher outcome sensitivity to described rewards and losses. From the temperamental characteristics, higher attentional focusing was linked with a higher learning rate on the experience-based task and a bias to accept gambles in the gain domain on the description-based task. Our findings demonstrate the importance of comparing children's behavior across qualitatively different tasks rather than studying a single behavior in isolation.

COMT Val/Met and Psychopathic Traits in Children and Adolescents: A Systematic Review and New Evidence of a Developmental Trajectory toward Psychopathy

Psychopathic traits in youth may lead to adult criminal behaviors/psychopathy. The Val158Met polymorphism of catechol-O-methyltransferase (COMT) may influence the risk for psychopathy-related behaviors, while acting as a biomarker for predicting treatment response to dopaminergic medications. The literature shows inconsistent findings, making the interpretation of COMT's role difficult. The aims of this article are (i) to conduct a systematic review to analyze the effects of COMT Val158Met on psychopathic traits in children and adolescents, and (ii) to present new evidence on the developmental trajectory of the association of Val158Met and youth psychopathic traits. For the systematic review, a literature search was conducted using PubMed, EMBASE, OVID Medline and PsychINFO with the search terms for psychopathic traits, Val158Met and age of interest. In our genotype study, the COMT Val158Met genotype of 293 youth with European ancestry was analyzed in association with the psychopathy-related behavior scores from the Child Behavior Checklist and the Psychopathy Screening Device. To examine the potential influence of developmental changes, the sample was split into at or above and below age 13, and analyses were performed in males and females separately. The literature search yielded twenty-eight articles to be included in the systematic review, which demonstrated mixed results on the association depending on environmental factors, sex ratios, age groups and behavioral disorder diagnoses. The results from our genotype study revealed that Met homozygous youth in the below age 13 group and conversely Val carrier youth in the above age 13 group were more likely to display psychopathic traits. To our knowledge, this is the first study to systematically review the effects of COMT Val158Met on psychopathic traits in childhood and adolescence, and to provide new evidence on the changing effects of Val158Met on psychopathy-related behaviors with development. Elucidating the role of the COMT genotype in conjunction with the child versus adolescent stage of development for psychopathic traits may help predict treatment response, and may lead to early intervention and prevention strategies.

A Dopamine Pathway Gene Risk Score for Cognitive Recovery Following Traumatic Brain Injury: Methodological Considerations, Preliminary Findings, and Interactions With Sex

OBJECTIVES

With evidence of sexual dimorphism involving the dopamine (DA)-pathway, and the importance of DA pathways in traumatic brain injury (TBI) recovery, we hypothesized that sex × DA-gene interactions may influence cognition post-TBI.

PARTICIPANTS

Adult survivors of severe TBI (n = 193) consecutively recruited from a level 1 trauma center.

DESIGN

Risk allele assignments were made for multiple DA pathway genes using a sex-specific stratified approach. Genetic risk alleles, and their impacts on cognition, were assessed at 6 and 12 months postinjury using unweighted, semiweighted, and weighted gene risk score (GRS) approaches.

MAIN MEASURES

A cognitive composite score generated from 8 standardized neuropsychological tests targeting multiple cognitive domains.

RESULTS

A significant sex × gene interaction was observed at 6 and 12 months for ANKK1 rs1800497 (6M: P = .002, 12M: P = .001) and COMT rs4680 (6M: P = .048; 12M: P = .004); DRD2 rs6279 (P = .001) and VMAT rs363226 (P = .043) genotypes were independently associated with cognition at 6 months, with trends for a sex × gene interaction at 12 months. All GRS methods were significant predictors of cognitive performance in multivariable models. Weighted GRS multivariate models captured the greatest variance in cognition: R = 0.344 (6 months); R = 0.441 (12 months), significantly increasing the variance captured from the base prediction models.

CONCLUSIONS

A sex-specific DA-pathway GRS may be a valuable tool when predicting cognitive recovery post-TBI. Future work should validate these findings and explore how DA-pathway genetics may guide therapeutic intervention.

Catechol-O-methyltransferase Val158Met polymorphism associates with affect and cortisol levels in women

Introduction

We tested the extent to which the catechol-O-methyltransferase (COMT) Val158Met polymorphism is associated with affective state and evening cortisol levels. We limited our study to women as previous research suggests that the link between COMT genotype and psychological health is entangled by sex differences.

Materials and Methods

The participants were assessed on measures of anxiety, mood disturbance, depressive symptomatology, and perceived stress. We also evaluated participants on a quality of life measures that included two emotion domains and two physical domains (physical health and environment).

Results

We found that under normal (nonstress) conditions, the COMT A allele (Met carriers, higher dopamine) associates with healthier affect and lower afternoon cortisol levels in women. These effects were limited to affective measures and not to physical or environmental quality of life.

Conclusions

These findings help to shed light on the complex nature of COMT and emotion, and suggest that both sex and task condition (stress vs. nonstress) should be considered when examining the relationship between COMT genotype and emotion.

Age, gender and deterrability: Are younger male drivers more likely to discount the future?

Utilizing the Classical Deterrence theory and Stafford and Warr's (1993) reconceptualized model of deterrence, the current study examined whether age, gender, and discounting the future tendencies influence perceptions of being apprehended for speeding offences. Licensed motorists (N=700; 57% female) in Queensland (Australia) were recruited to complete a self-report questionnaire that measured perceptual deterrence, speeding related behaviors and discounting the future tendencies. Data were analyzed utilizing descriptive, bivariate and multivariate regressions. Significant (albeit weak) positive correlations were found between age and perceptions of apprehension certainty. Males were significantly more likely to report higher incidences of speeding (including while avoiding detection) compared to females. In contrast, females were more likely to perceive high levels of apprehension certainty and consider impending penalties to be more severe. At a multivariate level, discounting the future tendencies (in addition to being male, reporting lower levels of perceptual severity and swiftness, and more instances of punishment avoidance) were predictive of lower perceptual certainty levels. This study is one of the first to reveal that being male and having a tendency to discount the consequences of the future may directly influence drivers' perceptual deterrence levels.

Risk Perception and Risk-Taking Behaviour during Adolescence: The Influence of Personality and Gender

This study investigated the influence of personality characteristics and gender on adolescents’ perception of risk and their risk-taking behaviour. Male and female participants (157 females: 116 males, aged 13–20) completed self-report measures on risk perception, risk-taking and personality. Male participants perceived behaviours as less risky, reportedly took more risks, were less sensitive to negative outcomes and less socially anxious than female participants. Path analysis identified a model in which age, behavioural inhibition and impulsiveness directly influenced risk perception, while age, social anxiety, impulsiveness, sensitivity to reward, behavioural inhibition and risk perception itself were directly or indirectly associated with risk-taking behaviour. Age and behavioural inhibition had direct relationships with social anxiety, and reward sensitivity was associated with impulsiveness. The model was representative for the whole sample and male and female groups separately. The observed relationship between age and social anxiety and the influence this may have on risk-taking behaviour could be key for reducing adolescent risk-taking behaviour. Even though adolescents may understand the riskiness of their behaviour and estimate their vulnerability to risk at a similar level to adults, factors such as anxiety regarding social situations, sensitivity to reward and impulsiveness may exert their influence and make these individuals prone to taking risks. If these associations are proven causal, these factors are, and will continue to be, important targets in prevention and intervention efforts.

COMT Val158Met polymorphism influences the susceptibility to framing in decision-making: OFC-amygdala functional connectivity as a mediator

Individuals tend to avoid risk in a gain frame, in which options are presented in a positive way, but seek risk in a loss frame, in which the same options are presented negatively. Previous studies suggest that emotional responses play a critical role in this "framing effect." Given that the Met allele of COMT Val158Met polymorphism (rs4680) is associated with the negativity bias during emotional processing, this study investigated whether this polymorphism is associated with individual susceptibility to framing and which brain areas mediate this gene-behavior association. Participants were genotyped, scanned in resting state, and completed a monetary gambling task with options (sure vs risky) presented as potential gains or losses. The Met allele carriers showed a greater framing effect than the Val/Val homozygotes as the former gambled more than the latter in the loss frame. Moreover, the gene-behavior association was mediated by resting-state functional connectivity (RSFC) between orbitofrontal cortex (OFC) and bilateral amygdala. Met allele carriers showed decreased RSFC, thereby demonstrating higher susceptibility to framing than Val allele carriers. These findings demonstrate the involvement of COMT Val158Met polymorphism in the framing effect in decision-making and suggest RSFC between OFC and amygdala as a neural mediator underlying this gene-behavior association. Hum Brain Mapp 37:1880-1892, 2016. © 2016 Wiley Periodicals, Inc.

Is risk-taking propensity a familial vulnerability factor for alcohol use? An examination in two independent samples

Research indicates that increased risk-taking propensity (RTP) is associated with higher alcohol use. There is also some evidence to suggest that it is not just a state factor or 'scar,' but instead a vulnerability factor. If this is the case, increased RTP should be evident in healthy individuals that are at risk for alcohol use. To date, few studies have examined whether RTP is a familial vulnerability factor and thus, the aim of the current study was to test whether RTP aggregates within families and if increased RTP is evident in biological family members at risk for alcohol use. Sample 1 included 87 biological, adult sibling pairs and Sample 2 included 111 biological mother and adolescent dyads (total N = 396). All participants completed a behavioral measure of RTP and were assessed for alcohol use. Results in both samples were strikingly consistent. In Sample 1, RTP was correlated among siblings and greater frequency of proband alcohol use predicted greater sibling RTP, over and above sibling alcohol use. In Sample 2, RTP was correlated among mothers and their offspring and greater maternal alcohol use problems predicted greater adolescent RTP over and above adolescent substance use. Together, these findings suggest that RTP may be a familial vulnerability factor for alcohol use as it aggregates within families and is increased in relatives of individuals with higher levels of alcohol use.

Replication study implicates COMT val158met polymorphism as a modulator of probabilistic reward learning

Previous studies suggest that a single nucleotide polymorphism in the catechol-O-methyltransferase (COMT) gene (val158met) may modulate reward-guided decision making in healthy individuals. The polymorphism affects dopamine catabolism and thus modulates prefrontal dopamine levels, which may lead to variation in individual responses to risk and reward. We previously showed, using tasks that index reward responsiveness (measured by responses bias towards reinforced stimuli) and risk taking (measured by the Balloon Analogue Risk Task), that COMT met homozygotes had increased reward responsiveness and, thus, an increased propensity to seek reward. In this study, we sought to replicate these effects in a larger, independent cohort of Caucasian UK university students and staff with similar demographic characteristics (n = 101; 54 females, mean age: 22.2 years). Similarly to our previous study, we observed a significant trial × COMT genotype interaction (P = 0.047; η(2) = 0.052), which was driven by a significant effect of COMT on the incremental acquisition of response bias [response bias at block 3 - block 1 (met/met > val/val: P = 0.028) and block 3 - block 2 (met/met > val/val: P = 0.007)], suggesting that COMT met homozygotes demonstrated higher levels of reward responsiveness by the end of the task. However, we failed to see main effects of COMT genotype on overall response bias or risk-seeking behaviour. These results provide additional evidence that prefrontal dopaminergic variation may have a role in reward responsiveness, but not risk-seeking behaviour. Our findings may have implications for neuropsychiatric disorders characterized by clinical deficits in reward processing such as anhedonia.

Risky decision-making and ventral striatal dopamine responses to amphetamine: a positron emission tomography [(11)C]raclopride study in healthy adults

Recent functional magnetic resonance imaging (fMRI) studies have provided compelling evidence that corticolimbic brain regions are integrally involved in human decision-making. Although much less is known about molecular mechanisms, there is growing evidence that the mesolimbic dopamine (DA) neurotransmitter system may be an important neural substrate. Thus far, direct examination of DA signaling in human risk-taking has centered on gambling disorder. Findings from several positron emission tomography (PET) studies suggest that dysfunctions in mesolimbic DA circuits may play an important role in gambling behavior. Nevertheless, interpretation of these findings is currently hampered by a need for better understanding of how individual differences in regional DA function influence normative decision-making in humans. To further our understanding of these processes, we used [(11)C]raclopride PET to examine associations between ventral striatal (VS) DA responses to amphetamine (AMPH) and risky decision-making in a sample of healthy young adults with no history of psychiatric disorder, Forty-five male and female subjects, ages 18-29 years, completed a computerized version of the Iowa Gambling Task. Participants then underwent two 90-minute PET studies with high specific activity [(11)C]raclopride. The first scan was preceded by intravenous saline; the second, by intravenous AMPH (0.3mg/kg). Findings of primary analyses showed that less advantageous decision-making was associated with greater right VS DA release; the relationship did not differ as a function of gender. No associations were observed between risk-taking and left VS DA release or baseline D2/D3 receptor availability in either hemisphere. Overall, the results support notions that variability in striatal DA function may mediate inter-individual differences in risky decision-making in healthy adults, further suggesting that hypersensitive DA circuits may represent a risk pathway in this population.

COMT-by-sex interaction effect on psychosis proneness

Schizotypy phenotypes in the general population share etiopathogenic mechanisms and risk factors with schizophrenia, supporting the notion of psychosis as a continuum ranging from nonclinical to clinical deviance. Catechol-O-methyltransferase (COMT) is a candidate susceptibility gene for schizophrenia that is involved in the regulation of dopamine in the prefrontal cortex. Several recent studies have reported a sex difference in the impact of COMT genotype on psychiatric and cognitive phenotypes and personality traits. The present study investigated the association of COMT Val158Met (rs4680) with psychometric positive and negative schizotypy and psychotic experiences in a sample of 808 nonclinical young adults. The main finding was that sex moderates the association of COMT genotype with the negative dimension of both schizotypy and psychotic experiences. Male subjects carrying the Val allele tended to score higher on the negative dimension of both trait and symptom-like measures. The results from the present study are consistent with recent work suggesting an association between negative schizotypy and diminished prefrontal dopamine availability. They support the idea that a biological differentiation underlies the positive and negative schizotypy dimensions. Additionally, these findings contribute to the growing literature on sex-specific effects of COMT on the predisposition to psychiatric disorders and personality traits.

Genetic predictor of working memory and prefrontal function in women with HIV

The Val158Met (rs4680) single-nucleotide polymorphism (SNP) of the catechol-O-methyltransferase gene (COMT) influences executive function and prefrontal function through its effect on dopamine (DA) metabolism. Both HIV and the Val allele of the Val158Met SNP are associated with compromised executive function and inefficient prefrontal function. The present study used behavioral and neuroimaging techniques to determine independent and interactive associations between HIV serostatus and COMT genotype on working memory and prefrontal function in women. For the behavioral study, 54 HIV-infected and 33 HIV-uninfected women completed the 0-, 1-, and 2-back conditions of the verbal N-back, a working memory test. For the imaging study, 36 women (23 HIV-infected, 13 HIV-uninfected) underwent functional magnetic resonance imaging (fMRI) assessments while completing the N-back task. HIV-infected women demonstrated significantly worse N-back performance compared with HIV-uninfected women (p < 0.05). A significant serostatus by genotype interaction (p < 0.01) revealed that, among Val/Val, but not Met allele carriers, HIV-infected women performed significantly worse than HIV-uninfected controls across N-back conditions (p < 0.01). Analogous to behavioral findings, a serostatus by genotype interaction revealed that HIV-infected Val/Val carriers showed significantly greater prefrontal activation compared with HIV-uninfected Val/Val carriers (p < 0.01). Conversely, HIV-uninfected Met allele carriers demonstrated significantly greater prefrontal activation compared with HIV-infected Met allele carriers. Findings suggest that the combination of HIV infection and the Val/Val COMT genotype leads to working memory deficits and altered prefrontal function in HIV-infected individuals.

The mediating effect of prefrontal asymmetry on the relationship between the COMT Val(158)Met SNP and trait consummatory positive affect

The Val(158)Met rs4680 polymorphism in the COMT gene regulates dopamine catabolism in the prefrontal cortex (PFC). Dopamine's involvement in reward experience suggests those with the methionine (Met) variant may exhibit trait-level sensitivity to reward due to more post-synaptic dopamine in the PFC. A physiological mediator of this association may be greater relative left asymmetry in the PFC, a putative biomarker for trait positive emotionality. Electroencephalograms of 120 participants were measured during a task that assesses two aspects of reward processing: pre-reward anticipation and post-reward consummatory affect. Participants provided genetics samples and completed the Temporal Experience of Pleasure Scale (TEPS), which assesses trait-level anticipatory and consummatory positive affect. Met carriers had higher TEPS-Consummatory scores. This effect was mediated by greater relative left activation in the post-reward phase of the task. No effects were observed for the pre-reward phase. Results suggest that frontal asymmetry is an endophenotype between COMT genotype and trait reward responsivity.

Adolescent brain maturation and smoking: what we know and where we're headed

Smoking is a leading cause of mortality and morbidity worldwide. Smoking initiation often occurs during adolescence. This paper reviews and synthesizes adolescent development and nicotine dependence literatures to provide an account of adolescent smoking from onset to compulsive use. We extend neurobiological models of adolescent risk-taking, that focus on the interplay between incentive processing and cognitive control brain systems, through incorporating psychosocial and contextual factors specific to smoking, to suggest that adolescents are more vulnerable than adults to cigarette use generally, but that individual differences exist placing some adolescents at increased risk for smoking. Upon smoking, adolescents are more likely to continue smoking due to the increased positive effects induced by nicotine during this period. Continued use during adolescence, may be best understood as reflecting drug-related changes to neural systems underlying incentive processing and cognitive control, resulting in decision-making that is biased towards continued smoking. Persistent changes following nicotine exposure that may underlie continued dependence are described. We highlight ways that interventions may benefit from a consideration of cognitive-neuroscience findings.

Temperament and character in remitted and symptomatic patients with schizophrenia: modulation by the COMT Val158Met genotype

While research on remission in schizophrenia has gained attention, personality characteristics associated with remission in schizophrenia have been under-studied. A functional valine-to-methionine (Val158Met) polymorphism in the catechol-O-methyltransferase (COMT) gene is shown to modify clinical presentation of schizophrenia despite weak or no association with the disorder itself. Studies also report that this polymorphism can affect personality traits. We aimed to examine personality traits of remitted patients with schizophrenia as compared to symptomatic patients and healthy controls and to investigate whether the COMT Val158Met polymorphism influences their personality. Scores on the Temperament and Character Inventory were compared between 34 remitted outpatients with schizophrenia, age- and sex-matched 72 symptomatic outpatients with schizophrenia, and matched 247 healthy individuals. The effect of COMT Val158Met polymorphism on personality was examined in each group. The analysis of covariance, controlling for confounding variables, revealed that compared to healthy controls, symptomatic patients exhibited a pervasively altered personality profile whereas remitted patients showed alterations in more limited personality dimensions and demonstrated normal levels of novelty-seeking, reward dependence and cooperativeness. The two-way analysis of covariance, with genotype and sex as between-subject factors and confounders as covariates, revealed that Met carriers demonstrated significantly lower reward dependence and cooperativeness than Val homozygotes in symptomatic patients; while no significant genotype effect was found in remitted patients or in healthy individuals. These findings indicate that remitted patients with schizophrenia have a relatively adaptive personality profile compared to symptomatic patients. The COMT Val158Met polymorphism might have a modulating effect on the relationship between personality and remission.

Gene-sex interactions in schizophrenia: focus on dopamine neurotransmission

Schizophrenia is a severe mental disorder, with a highly complex and heterogenous clinical presentation. Our current perspectives posit that the pathogenic mechanisms of this illness lie in complex arrays of gene × environment interactions. Furthermore, several findings indicate that males have a higher susceptibility for schizophrenia, with earlier age of onset and overall poorer clinical prognosis. Based on these premises, several authors have recently begun exploring the possibility that the greater schizophrenia vulnerability in males may reflect specific gene × sex (G×S) interactions. Our knowledge on such G×S interactions in schizophrenia is still rudimentary; nevertheless, the bulk of preclinical evidence suggests that the molecular mechanisms for such interactions are likely contributed by the neurobiological effects of sex steroids on dopamine (DA) neurotransmission. Accordingly, several recent studies suggest a gender-specific association of certain DAergic genes with schizophrenia. These G×S interactions have been particularly documented for catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO), the main enzymes catalyzing DA metabolism. In the present review, we will outline the current evidence on the interactions of DA-related genes and sex-related factors, and discuss the potential molecular substrates that may mediate their cooperative actions in schizophrenia pathogenesis.

HIV serostatus differs by catechol-O-methyltransferase Val158Met genotype

OBJECTIVE

The Met allele of the catechol-O-methyltransferase (COMT) Val158Met polymorphism is associated with increased cortical dopamine and risk behaviors including illicit drug use and unprotected sex. Therefore, we examined whether or not the distribution of the Val158Met genotype differed between HIV-infected and HIV-uninfected women.

DESIGN

Cross-sectional analysis using data from the Women's Interagency HIV Study (WIHS), the largest longitudinal cohort study of HIV in women.

METHODS

We conducted an Armitage-Cochran test and logistic regression to compare genotype frequencies between 1848 HIV-infected and 612 HIV-uninfected women in WIHS.

RESULTS

The likelihood of carrying one or two Met alleles was greater in HIV-infected women (61%) compared to HIV-uninfected women (54%), Z  =  -3.60, P  < 0.001.

CONCLUSION

We report the novel finding of an association between the Val158Met genotype and HIV serostatus that may be mediated through the impact of dopamine function on propensity for risk-taking.

Gene-environment interaction on cognition: a twin study of childhood maltreatment and COMT variability

The functional variant Val(158)Met in the coding sequence of COMT gene is involved in the modulation of dopamine availability in the prefrontal cortex in both clinical and general population samples. It has been suggested that the interplay between this genotype and early environmental factors could be used to predict the observed variation in cognitive flexibility. However, other genetic variants and environmental factors may confound the association and produce the inconsistent results commonly found in the literature. In the present study we aimed at testing putative interaction mechanisms between childhood maltreatment and COMT genotypic variability that might explain a proportion of the observed variability of cognitive flexibility in the population. Our design was based on a sample of adult monozygotic twins, which allowed us to test these effects free from potential genetic and shared-environmental confounding factors. Results showed that unique environmental effects of childhood maltreatment significantly impacted cognitive performance among Met/Met subjects. Interestingly, the direction of the association indicated that exposure to early stressful experiences was associated with enhanced cognitive flexibility in this genotype group. These results suggest that COMT may operate as a plasticity gene that provides differential cognitive capacity to respond to environmental stressors.

Biological contributions to addictions in adolescents and adults: prevention, treatment, and policy implications

PURPOSE

Despite significant advances in our understanding of the biological bases of addictions, these disorders continue to represent a huge public health burden that is associated with substantial personal suffering. Efforts to target addictions require consideration of how the improved biological understanding of addictions may lead to improved prevention, treatment, and policy initiatives.

METHOD

In this article, we provide a narrative review of current biological models for addictions with a goal of placing existing data and theories within a translational and developmental framework targeting the advancement of prevention, treatment, and policy strategies.

RESULTS

Data regarding individual differences, intermediary phenotypes, and main and interactive influences of genetic and environmental contributions in the setting of developmental trajectories that may be influenced by addictive drugs or behavior indicate complex underpinnings of addictions.

CONCLUSIONS

Consideration and further elucidation of the biological etiologies of addictions hold significant potential for making important gains and reducing the public health impact of addictions.

COMT val158met predicts reward responsiveness in humans

A functional variant of the catechol-O-methyltransferase (COMT) gene [val158met (rs4680)] is frequently implicated in decision-making and higher cognitive functions. It may achieve its effects by modulating dopamine-related decision-making and reward-guided behaviour. Here we demonstrate that individuals with the met/met polymorphism have greater responsiveness to reward than carriers of the val allele and that this correlates with risk-seeking behaviour. We assessed performance on a reward responsiveness task and the Balloon analogue risk task, which measure how participants (N = 70, western European, university and postgraduate students) respond to reward and take risks in the presence of available reward. Individuals with the met/met genotype (n = 19) showed significantly higher reward responsiveness, F2,64 = 4.02, P = 0.02, and reward-seeking behaviour, F(2,68) = 4.52, P = 0.01, than did either val/met (n = 25) or val/val (n = 26) carriers. These results highlight a scenario in which genotype-dependent reward responsiveness shapes reward-seeking, therefore suggesting a novel framework by which COMT may modulate behaviour.