Gene-environment interaction in problematic substance use: interaction between DRD4 and insecure attachments

Candidate gene-environment interactions in substance abuse: A systematic review

BACKGROUND

The abuse of psychogenic drugs can lead to multiple health-related problems. Genetic and environmental vulnerabilities are factors in the emergence of substance use disorders. Empirical evidence regarding the gene-environment interaction in substance use is mixed. Summaries of the latest findings from a candidate gene approach will be useful for revealing the significance of particular gene contributions. Thus, we aim to identify different gene-environment interactions in patterns of substance use and investigate whether any effects trend notably across different genders and races.

METHODS

We reviewed published studies, until March 1, 2022, on substance use for candidate gene-environment interaction. Basic demographics of the included studies, target genes, environmental factors, main findings, patterns of gene-environment interaction, and other relevant information were collected and summarized.

RESULTS

Among a total of 44 studies, 38 demonstrated at least one significant interaction effect. About 61.5% of studies on the 5-HTTLPR gene, 100% on the MAOA gene, 42.9% on the DRD2 gene, 50% on the DRD4 gene, 50% on the DAT gene, 80% on the CRHR1 gene, 100% on the OPRM1 gene, 100% on the GABRA1 gene, and 50% on the CHRNA gene had a significant gene-environment interaction effect. The diathesis-stress model represents a dominant interaction pattern (89.5%) in the studies with a significant interaction effect; the remaining significant effect on substance use is found in the differential susceptibility model. The social push and swing model were not reported in the included studies.

CONCLUSION

The gene-environment interaction research on substance use behavior is methodologically multidimensional, which causes difficulty in conducting pooled analysis, or stated differently-making it hard to identify single sources of significant influence over maladaptive patterns of drug taking. In decreasing the heterogeneity and facilitating future pooled analysis, researchers must (1) replicate the existing studies with consistent study designs and measures, (2) conduct power calculations to report gene-environment correlations, (3) control for covariates, and (4) generate theory-based hypotheses with factorial based experiments when designing future studies.

Does parental separation moderate the heritability of health risk behavior among adolescents?

Social influences on adolescents' health risk behavior are well documented, but little is known about the interaction of parental separation with genetic sensitivities. Using data from a German sample of 1762 twins, this study examines whether family living arrangements moderate the influence of genetic predispositions on health risk behavior. Derived from variance decomposition moderator models, three key findings emerge. Firstly, genetic contributions to drug use are significantly higher in single-mother families, indicating an amplified heritability potentially resulting from triggered genetic sensitivities or challenges in preventing genetic risks from unfolding. Secondly, unique environmental factors have a greater impact on drug use in single-mother families. Lastly, no heritability differences are found in smoking and excessive alcohol consumption between family types. These findings provide novel evidence of increased importance of genetic influences on drug use in single-mother families, shedding light on gene-environment interactions, and informing policy interventions that support vulnerable family arrangements.

ADHD co-morbidities: A review of implication of gene × environment effects with dopamine-related genes

ADHD is a major burden in adulthood, where co-morbid conditions such as depression, substance use disorder and obesity often dominate the clinical picture. ADHD has substantial shared heritability with other mental disorders, contributing to comorbidity. However, environmental risk factors exist but their interaction with genetic makeup, especially in relation to comorbid disorders, remains elusive. This review for the first time summarizes present knowledge on gene x environment (GxE) interactions regarding the dopamine system. Hitherto, mainly candidate (GxE) studies were performed, focusing on the genes DRD4, DAT1 and MAOA. Some evidence suggest that the variable number tandem repeats in DRD4 and MAOA may mediate GxE interactions in ADHD generally, and comorbid conditions specifically. Nevertheless, even for these genes, common variants are bound to suggest risk only in the context of gender and specific environments. For other polymorphisms, evidence is contradictory and less convincing. Particularly lacking are longitudinal studies testing the interaction of well-defined environmental with polygenic risk scores reflecting the dopamine system in its entirety.

Early parent-child interactions and substance use disorder: An attachment perspective on a biopsychosocial entanglement

This review aims to elucidate environmental and genetic factors, as well as their epigenetic and neuroendocrine moderators, that may underlie the association between early childhood experiences and Substance Use Disorders (SUD), through the lens of parental attachment. Here we review those attachment-related studies that examined the monoaminergic systems, the hypothalamic pituitary adrenal stress response system, the oxytoninergic system, and the endogenous opioid system from a genetic, epigenetic, and neuroendocrine perspective. Overall, the selected studies point to a moderating effect of insecure attachment between genetic vulnerability and SUD, reasonably through epigenetic modifications. Preliminary evidence suggests that vulnerability to SUDs is related with hypo-methylation (e.g. hyper-expression) of high-risk polymorphisms on the monoaminergic and hypothalamic pituitary adrenal system and hyper-methylation (e.g. hypo-expressions) of protective polymorphisms on the opioid and oxytocin system. These epigenetic modifications may induce a cascade of neuroendocrine changes contributing to the subclinical and behavioural manifestations that precede the clinical onset of SUD. Protective and supportive parenting could hence represent a key therapeutic target to prevent addiction and moderate insecure attachment.

Association between Polymorphism rs1799732 of DRD2 Dopamine Receptor Gene and Personality Traits among MMA Athletes

Four factors—namely, harm avoidance, novelty seeking, reward addiction and persistence—represent the nature of temperament that is not genetically determined in itself. It was shown in earlier studies that a strong propensity to look for novelty or a tendency to engage in risky behavior is correlated with genetic variants in the area of the genes encoding dopamine receptors. Therefore, the aim of this study is to determine whether there is a relationship between personality traits and genetic variants in the area of the DRD2 dopamine receptor gene in MMA athletes. The participants consisted of 85 mixed martial arts (MMA) athletes and 284 healthy, non-MMA male participants. Their personality traits were measured using the Revised Temperament and Character Inventory. Blood was collected for genetic assays and all samples were genotyped using the real-time PCR method. We observed a statistically significant effect of a complex factor of the DRD2 rs1799732 genotype on MMA participants’ control and reward dependence. Engaging in high-risk sport may be associated with several personality characteristics. The DRD2 rs1799732 polymorphism may be associated with reduced harm avoidance in martial arts athletes, thereby modulating athletes’ predisposition to participate in high-risk sport.

Parsing out the role of dopamine D4 receptor gene (DRD4) on alcohol-related phenotypes: A meta-analysis and systematic review

Genetics account for moderate variation of individual differences in developing alcohol use disorder (AUD), but it is unclear which genetic variations contribute to AUD risk. One candidate gene investigated due to its association with AUD is the dopamine D4 receptor gene (DRD4), which contains a 48-base pair variable number tandem repeat (VNTR) in exon 3 of its coding region. To date, no quantitative synthesis of the published literature on the effects of DRD4 VNTR variation on alcohol-related phenotypes has been conducted. MEDLINE, Embase, Web of Science, and PsycInfo were searched for studies that reported on alcohol craving, alcohol consumption, severity of AUD, and case-control (AUD versus no diagnosis of AUD) studies in DRD4L (seven repeats or more) carriers compared with DRD4S (six repeats or less) homozygotes. Random-effects meta-analysis was used for all analyses. A pooled sample size of 655 to 13,360 of 28 studies were included. Compared with DRD4S homozygotes, DRD4L carriers had increased number of drinking days (SMD: 0.205; 95% CI: 0.008 to 0.402), binge drinking days (SMD: 0.217; 95% CI: 0.0532 to 0.380), and severity of AUD (SMD: 0.143; 95% CI: 0.028 to 0.259). There was no difference between DRD4 VNTR genotypes on drinks per drinking day, largest number of drinks per day/occasion, and case-control analysis. It was not possible to conduct a meta-analysis of the craving data, but a systematic review of this literature found mixed results on DRD4 VNTR genotype effect. The present meta-analysis suggests DRD4 VNTR variation may be a risk factor for problematic alcohol use. Our findings are limited, however, by the absence of ancestry data from studies included in our analysis, precluding our ability to adjust for population stratification. Due to the likelihood of type I error in candidate gene approaches, our work highlights the critical need for studies with larger and more inclusive samples that account for sex and genetic ancestry to fully understand this relationship.

A systematic review: Candidate gene and environment interaction on alcohol use and misuse among adolescents and young adults

BACKGROUND AND OBJECTIVES

Youth drinking is a pervasive public health concern with serious negative developmental implications. Candidate gene and environment interaction studies (cGxE) show that environmental effects on drinking behaviors may differ by individuals' genotypes. Yet little is known about whether genetic and environmental effects on drinking behaviors are developmentally specific.

METHODS

This systematic review evaluated 42 cGxE studies of drinking in adolescence and young adulthood.

RESULTS

Although there are mixed findings, studies of cGxE effects involving DRD4, 5-HTTLPR, DRD2, and OPRM1 genotypes showed relatively consistent patterns. The effects of under-controlled environments (eg, low levels of parental monitoring) on early and middle adolescent drinking appeared to differ across DRD2 or OPRM1 genotypes. Effects of alcohol-facilitating environments (eg, heavy drinking peers) on late adolescent and young adult drinking appeared to differ across DRD4 or OPRM1 genotypes. Interactions between 5-HTTLPR genotype with stressful environments (eg, negative life events) were found throughout adolescence and young adulthood, although there were some inconsistencies regarding the risk-conferring allele. There was limited evidence for other cGxE effects due to the small number of studies.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

This review suggests that GxE findings may advance our knowledge regarding which developmentally specific conditions result in the expression of candidate genes that influence youth alcohol use and misuse. However, since a significant number of studies had small sample sizes and most studies had small effect sizes, findings need replication across independent studies with large samples. (Am J Addict 2018;XX:1-19).

A meta-analysis of longitudinal associations between substance use and interpersonal attachment security

Substance use has long been associated with close relationship distress. Although the direction of influence for this association has not been established, it has often been assumed that substance use is the causal agent and that close relationship distress is the effect. But research seeking to establish temporal precedence in this link has produced mixed findings. Further, theoretical models of substance use and close relationship processes present the plausibility of the inverse pathway-that insecure close relationships may serve as a vulnerability factor for the development of later substance problems. The current review applies an attachment-theoretical framework to the association between close social bonds and substance use and substance-related problems. Targeting longitudinal studies of attachment and substance use, we examined 665 effect sizes drawn from 34 samples (total N = 56,721) spanning time frames ranging from 1 month to 20 years (M = 3.8 years). Results revealed a significant prospective correlation between earlier attachment and later substance use (r = -.11, 95% CI [-.14, -0.08]). Further, cross-lagged coefficients were calculated which parsed auto-regressive effects, indicating that lower attachment security temporally preceded increases in substance use (r = -.05, 95% CI [-.06, -.04]). Analyses further indicated that the pathway from earlier attachment to later substance use was significantly stronger than that from earlier substance use to later attachment. Results also revealed several moderators of the attachment-substance use link. These findings suggest that insecure attachment may be a vulnerability factor for substance use, and indicate close relationship quality as a promising line of inquiry in research on substance use disorder risk. (PsycINFO Database Record

Cannabis use by women during pregnancy does not influence infant DNA methylation of the dopamine receptor DRD4

Background: Maternal cannabis use in pregnancy is linked with long-term adverse behavioral outcomes in offspring. Epigenetic processes established in utero that affect dopaminergic (reward) signaling may mediate risks. Associations between cannabis use and offspring DNA methylation have not been investigated; however, maternal tobacco smoking in pregnancy is associated with distinct patterns of DNA methylation at birth and beyond. Objectives: To determine whether maternal cannabis use is associated with methylation of the dopamine receptor gene DRD4 promoter in infants. Methods: Mothers in the Triple B study provided detailed information on drug use in each trimester of pregnancy. Buccal swabs were collected from neonates at 8 weeks (n = 804, 51.7% male, and 48.3% female). DRD4 promoter DNA methylation was measured using SEQUENOM MassARRAY. Results: Fifty-seven of the women in the study reported drug use during pregnancy, of whom 44 used cannabis. Of 19 cytosine-phosphate-guanine dinucleotides (CpG) units tested in DRD4, gestational cannabis use was associated with offspring methylation at 1 CpG unit in multivariate models (β + 1.48, CI: 0.02 to 2.93, and p = 0.047). At another site there was weak evidence that both cannabis and other drug use were independently associated with increased methylation, while the association with tobacco was in the reverse direction (cannabis use β + 0.67, CI: −0.12 to 1.46, and p = 0.09; other drug use β + 1.11, CI: 0.17 to 2.05, and p = 0.02; tobacco use β −0.41, CI: −0.85 to 0.03, and p = 0.07). None of the associations would remain significant after correction for multiple testing. Conclusion: There is no strong evidence that maternal cannabis use in pregnancy is associated with offspring DRD4 methylation.

Evidence for a Link Between Fkbp5/FKBP5, Early Life Social Relations and Alcohol Drinking in Young Adult Rats and Humans

Alcohol misuse has been linked to dysregulation of stress, emotion, and reward brain circuitries. A candidate key mediator of this association is the FK506-binding protein (FKBP5), a negative regulator of the glucocorticoid receptor. The aim of the present study was to further understand the Fkbp5/FKBP5-related genetic underpinnings underlying the relationship between early life social relations and alcohol drinking. The effect of maternal separation and voluntary alcohol drinking on Fkbp5 expression was investigated in the brain of young adult rats, whereas the interaction effect of the functional FKBP5 single nucleotide polymorphism rs1360780 genotype and parent-child relationship on problematic drinking was examined in young adult humans. In rats, Fkbp5 expression in the nucleus accumbens and ventral tegmental area, core regions of the reward system, was affected in a region-dependent manner and in opposite direction by maternal separation and alcohol drinking. Fkbp5 expression in the cingulate cortex was affected by the combined effect of maternal separation and alcohol drinking. In humans, the TT genotype, in the presence of a poor relationship between the child and parents, was associated with problematic drinking behavior. The present findings suggest that Fkbp5 expression in mesocorticolimbic dopaminergic regions associates with early life stress-mediated sensitivity to alcohol drinking and that FKBP5 genotype interacts with parent-child relationship to influence alcohol drinking. These findings are the first to point to a role of FKBP5 in propensity to alcohol misuse and call for studies of the underlying molecular mechanisms to identify potential drug targets.

Genetic and Environmental Interplay in Adolescent Substance Use Disorders

Adolescent substance use is of considerable public health importance. This narrative review provides a brief background to genetically informative research methodologies and highlights key recent literature examining the interplay between genetic and environmental influences in the etiology of substance use. Twin studies have quantified the magnitude of genetic and environmental influences, and more recently co-relative and Children of Twin designs have shown environments can moderate heritability. Studies have identified a number of specific gene variants (e.g. OPRM1, DRD4, 5HTTLPR) that interact with parenting and peer influence, and the effectiveness of interventions may vary by genotype. However, little research has taken into account the stage-sequential nature of substance use. This may obscure important differences in the genetic and environmental influences, and their interplay, at the stages of escalation to problem use. Future research needs to build on existing methodologies to disentangle the complexities of progression in adolescent substance use.

Neurogenetic and epigenetic correlates of adolescent predisposition to and risk for addictive behaviors as a function of prefrontal cortex dysregulation

As addiction professionals, we are becoming increasingly concerned about preteenagers and young adults' involvement with substance abuse as a way of relieving stress and anger. The turbulent underdeveloped central nervous system, especially in the prefrontal cortex (PFC), provides impetus to not only continue important neuroimaging studies in both human and animal models, but also to encourage preventive measures and cautions embraced by governmental and social media outlets. It is well known that before people reach their 20s, PFC development is undergoing significant changes and, as such, hijacks appropriate decision making in this population. We are further proposing that early genetic testing for addiction risk alleles will offer important information that could potentially be utilized by their parents and caregivers prior to use of psychoactive drugs by these youth. Understandably, family history, parenting styles, and attachment may be modified by various reward genes, including the known bonding substances oxytocin/vasopressin, which effect dopaminergic function. Well-characterized neuroimaging studies continue to reflect region-specific differential responses to drugs and food (including other non-substance-addictive behaviors) via either "surfeit" or "deficit." With this in mind, we hereby propose a "reward deficiency solution system" that combines early genetic risk diagnosis, medical monitoring, and nutrigenomic dopamine agonist modalities to combat this significant global dilemma that is preventing our youth from leading normal productive lives, which will in turn make them happier.

Increased brain activity to unpleasant stimuli in individuals with the 7R allele of the DRD4 gene

The aim of the study was to examine functional brain activity in response to unpleasant images in individuals with the 7-repeat (7R) allele compared to individuals with the 4-repeat (4R) allele of the dopamine receptor D4 (DRD4) gene (VNTR in exon 3). Based on the response ready hypothesis, individuals with the DRD4-4R/7R genotype were expected to show greater functional brain activity in response to unpleasant compared to neutral stimuli in specific regions of the frontal, temporal, parietal and limbic lobes, which form the networks involved in attentional, emotional, and preparatory responses. Functional Magnetic Resonance Imaging activity was studied in 26 young adults (13 with the DRD4-4R/7R genotype and 13 with the DRD4-4R/4R genotype). Participants were asked to look at and subjectively rate unpleasant and neutral images. Results showed increased brain activity in response to unpleasant images compared to neutral images in the right temporal lobe in participants with the DRD4-4R/7R genotype versus participants with the DRD4-4R/4R genotype. The increase in right temporal lobe activity in individuals with DRD4-4R/7R suggests greater involvement in processing negative emotional stimuli. Intriguingly, no differences were found between the two genotypes in the subjective ratings of the images. The findings corroborate the response ready hypothesis, which suggests that individuals with the 7R allele are more responsive to negative emotional stimuli compared to individuals with the 4R allele of the DRD4 gene.

A longitudinal analysis of the effects of a DRD4 polymorphism on marijuana use

The current study used a variable- and person-centered approach to examine whether a DRD4 polymorphism explained within-individual differences in frequency of marijuana use from adolescence into emerging adulthood. Data were analyzed from 1897 respondents from the genetic subsample of the National Longitudinal Study of Adolescent Health (Add Health) at waves I (ages 13-17), II (ages 14-18), and III (ages 21-25). Latent class growth model results revealed that marijuana use was characterized by four trajectories (non-users/experimenters, increasers, desisters, and chronic users), and that the DRD4 polymorphism differentiated increasers from non-users/experimenters. Overall, the results suggested that the DRD4 polymorphism may be relevant to differences in the developmental trajectories of marijuana use.

DRD4 genotype predicts longevity in mouse and human

Longevity is influenced by genetic and environmental factors. The brain's dopamine system may be particularly relevant, since it modulates traits (e.g., sensitivity to reward, incentive motivation, sustained effort) that impact behavioral responses to the environment. In particular, the dopamine D4 receptor (DRD4) has been shown to moderate the impact of environments on behavior and health. We tested the hypothesis that the DRD4 gene influences longevity and that its impact is mediated through environmental effects. Surviving participants of a 30-year-old population-based health survey (N = 310; age range, 90-109 years; the 90+ Study) were genotyped/resequenced at the DRD4 gene and compared with a European ancestry-matched younger population (N = 2902; age range, 7-45 years). We found that the oldest-old population had a 66% increase in individuals carrying the DRD4 7R allele relative to the younger sample (p = 3.5 × 10(-9)), and that this genotype was strongly correlated with increased levels of physical activity. Consistent with these results, DRD4 knock-out mice, when compared with wild-type and heterozygous mice, displayed a 7-9.7% decrease in lifespan, reduced spontaneous locomotor activity, and no lifespan increase when reared in an enriched environment. These results support the hypothesis that DRD4 gene variants contribute to longevity in humans and in mice, and suggest that this effect is mediated by shaping behavioral responses to the environment.