Commentary on 'The case for gene-environment interactions in psychiatry'

The serotonin transporter promoter polymorphism moderates the continuity of behavioral inhibition in early childhood

Persistently elevated behavioral inhibition (BI) in children is a marker of vulnerability to psychopathology. However, little research has considered the joint influences of caregiver and child factors that may moderate the continuity of BI in early childhood, particularly genetic variants that may serve as markers of biological plasticity, such as the serotonin transporter linked polymorphic region (5-HTTLPR). We explored this issue in 371 preschoolers and their caregivers, examining whether parent characteristics (i.e., overinvolvement or anxiety disorder) and child 5-HTTLPR influenced the continuity of BI between ages 3 and 5. Measures were observational ratings of child BI, observational and questionnaire measures of parenting, and parent interviews for anxiety disorder history, and children were genotyped for the 5-HTTLPR. Parent factors did not moderate the association between age 3 and age 5 BI; however, child BI at age 3 interacted with children's 5-HTTLPR variants to predict age 5 BI, such that children with at least one copy of the short allele exhibited less continuity of BI over time relative to children without this putative plasticity variant. Findings are consistent with previous work indicating the 5-HTTLPR short variant increases plasticity to contextual influences, thereby serving to decrease the continuity of BI in early childhood.

Self-regulatory failure and the perpetration of adolescent dating violence: Examining an alcohol use by gene explanation

Studies report that alcohol use is related to partner violence, but for many, alcohol use does not culminate in violence against partners. Guided by a self-regulatory failure framework, we predicted that alcohol use would be more strongly associated with dating violence perpetration among adolescents with genotypes linked to impulsivity and emotional reactivity. The hypothesis was tested using random coefficient modeling of data from a multi-wave longitudinal study spanning grades 8-12 (ages 13-18) (n = 1,475). Analyses adjusted for multiple testing and race, and the potential for gene by environment correlation was examined. As predicted, alcohol use was more strongly associated with dating violence among adolescents who had a high rather than a low multilocus genetic profile composed of five genetic markers that influence dopamine signaling. Alcohol use was more strongly related to dating violence among boys with long rather than short 5-HTTLPR alleles, the opposite of the prediction. MAOA-uVNTR did not interact with alcohol, but it had a main effect on dating violence by boys in later grades in the expected direction: boys with more low activity alleles perpetrated more dating violence. Exploratory analyses found variation in findings by race. Our findings demonstrate the importance of incorporating genes into etiological studies of adolescent dating violence, which to date has not been done. Aggr. Behav. Aggr. Behav. 42:189-203, 2015. © 2014 Wiley Periodicals, Inc.

From men to mice: CHRNA5/CHRNA3, smoking behavior and disease

INTRODUCTION

The nicotinic acetylcholine receptor (nAChR) gene cluster CHRNA5-A3-B4 on chromosome 15 has been the subject of a considerable body of research over recent years. Two highly correlated single nucleotide polymorphisms (SNPs) within this region--rs16969968 in CHRNA5 and rs1051730 in CHRNA3--have generated particular interest.

METHODS

We reviewed the literature relating to SNPs rs16969968 and rs1051730 and smoking-related phenotypes, and clinical and preclinical studies, which shed light on the mechanisms underlying these associations.

RESULTS

Following the initial discovery of an association between this locus and smoking behavior, further associations with numerous phenotypes have been subsequently identified, including smoking-related behaviors, diseases, and cognitive phenotypes. Potential mechanisms thought to underlie these have also been described, as well as possible gene × environment interaction effects.

CONCLUSIONS

Perhaps counter to the usual route of scientific inquiry, these initial findings, based exclusively on human samples and strengthened by their identification through agnostic genome-wide methods, have led to preclinical research focused on determining the mechanism underlying these associations. Progress has been made using knockout mouse models, highlighting the importance of α5 nAChR subunits in regulating nicotine intake, particularly those localized to the habenula-interpeduncular nucleus pathway. Translational research seeking to evaluate the effect of nicotine challenge on brain activation as a function of rs16969968 genotype using neuroimaging technologies is now called for, which may point to new targets for novel smoking cessation therapies.

ORCHIDS: an observational randomized controlled trial on childhood differential susceptibility

BACKGROUND

A central tenet in developmental psychopathology is that childhood rearing experiences have a major impact on children's development. Recently, candidate genes have been identified that may cause children to be differentially susceptible to these experiences (i.e., susceptibility genes). However, our understanding of the differential impact of parenting is limited at best. Specifically, more experimental research is needed. The ORCHIDS study will investigate gene-(gene-)environment interactions to obtain more insight into a) moderating effects of polymorphisms on the link between parenting and child behavior, and b) behavioral mechanisms that underlie these gene-(gene-)environment interactions in an experimental design.

METHODS/DESIGN

The ORCHIDS study is a randomized controlled trial, in which the environment will be manipulated with an intervention (i.e., Incredible Years parent training). In a screening, families with children aged 4-8 who show mild to (sub)clinical behavior problems will be targeted through community records via two Dutch regional healthcare organizations. Assessments in both the intervention and control condition will be conducted at baseline (i.e., pretest), after 6 months (i.e., posttest), and after 10 months (i.e., follow-up).

DISCUSSION

This study protocol describes the design of a randomized controlled trial that investigates gene-(gene-)environment interactions in the development of child behavior. Two hypotheses will be tested. First, we expect that children in the intervention condition who carry one or more susceptibility genes will show significantly lower levels of problem behavior and higher levels of prosocial behavior after their parent(s) received the Incredible Years training, compared to children without these genes, or children in the control group. Second, we expect that children carrying one or more susceptibility genes will show a heightened sensitivity to changes in parenting behaviors, and will manifest higher emotional synchronization in dyadic interchanges with their parents. This may lead to either more prosocial behavior or antisocial behavior depending on their parents' behavior.

TRIAL REGISTRATION

Dutch Trial Register (NTR3594).

Risky alcohol use in adolescence: the role of genetics (DRD2, SLC6A4) and coping motives

BACKGROUND

Drinking to cope (i.e., drinking to forget or alleviate negative feelings) has been found to be associated with adolescents' heavy drinking and alcohol-related problems. Additionally, it is widely accepted that genetic factors are involved in alcohol use and dependence. Studies are only beginning to reveal, however, which specific genotypes are related to drinking behaviors, and it is unknown whether they may interact with coping motives in predicting adolescents' risky drinking. The aim of this study was to examine relationships between the dopamine D2 receptor gene (DRD2) Taq1A polymorphism (rs1800497), a serotonin transporter gene (SLC6A4) polymorphism (5-HTTLPR), coping motives, and adolescents' binge drinking and alcohol-related problems.

METHODS

Participants in this cross-sectional study were 282 Dutch adolescents (mean age 17.4, 47% men) who had consumed alcohol at least once in their life.

RESULTS

Coping motives were positively related to both binge drinking and alcohol-related problems, while DRD2 and SLC6A4 genotypes were not. DRD2, but not the SLC6A4 genotype, interacted with coping motives. The link between coping motives and alcohol outcomes was stronger among those carrying the DRD2 risk (A1) allele.

CONCLUSIONS

This study extends the present literature by providing additional insight into the etiological factors of adolescent drinking behavior. An interaction between a vulnerability gene (DRD2) and a cognitive factor (coping drinking) was found to be related to adolescents' binge drinking and alcohol-related problems.

Gene-environment interactions and alcohol use and dependence: current status and future challenges

AIM

To discuss the current status of gene-environment interaction research with regard to alcohol use and dependence. Further, we highlight the difficulties concerning gene-environment studies.

METHODS

Overview of the current evidence for gene-environment interactions in alcohol outcomes, and of the associated challenges in gene-environment studies.

RESULTS

Attention to the causative roles of gene-environment interactions in alcohol use and dependence is increasing. Studies with twin designs are beginning to examine gene-shared environment effects, and animal studies have investigated gene-environment interaction effects on alcohol intake in primates. Thirteen studies incorporated gene-environment interactions in examining alcohol use or dependence in humans. These studies held a variety of candidate genes and environmental risk factors and their heterogeneity made it impossible to draw firm general conclusions.

CONCLUSIONS

Challenges for future gene-environment studies are abundant, and consist of, for example, the development of clear theoretical assumptions about neurobiological mechanisms and the recruitment of large longitudinal samples that already start in childhood. Replication is essential to prevent an overload of false-positive results. Despite the difficulties, it is crucial to include gene-environment interactions in future studies in order to unravel the aetiological factors of human alcohol outcomes.