Genetic and environmental influences on externalizing behavior and alcohol problems in adolescence: a female twin study

Prevalence and heritability of alcohol use disorders in 18-year old Swedish twins

Background: Heritability of alcohol use disorders (AUDs) varies widely, with reported estimates of 30-78% in twin studies. This variation might be due to methodological differences (e.g., using different thresholds for AUDs, age differences between samples). Aim: To investigate the heritability of AUDs in a nation-wide sample of male and female twins in late adolescence (18 years). Participants: The study is based on data from 8,330 18-year-old Swedish monozygotic (MZ) and dizygotic (DZ) twins from the Child and Adolescent Twin Study (Sweden). Method: Univariate sex-limitation twin analyses were performed using (a) total AUDIT score, (b) different AUDIT cut-offs (AUDIT-10: potentially harmful alcohol use and most likely alcohol dependent ; AUDIT-C: potential hazardous alcohol consumption/active alcohol use disorders), and (c) a risk-group classification for alcohol dependence based on AUDIT total score. Results: Prevalence of potential hazardous alcohol consumption/active alcohol use was 57.1%, and for potentially harmful alcohol use prevalence was 26.5%. Prevalence was higher among females (59.0% and 31.1% respectively) than males (54.4% and 20.0% respectively). Overall, the results of the univariate model fitting indicated that there were qualitative sex differences in the genetic and environmental influences on AUDs, with generally moderate heritability estimates ranging between 0.37 and 0.50. Discussion: At odds with previous research, a harmful/hazardous drinking pattern was more common in this age group among females than a low-risk drinking pattern (where males were overrepresented). Heritability estimates were moderate throughout all measures and cut-offs, with equally high contributions from shared and non-shared environment. Sex-limitation models revealed qualitative sex differences for AUDs, suggesting that different genetic and/or environmental factors influence variation in AUDs in males and females.

A Systematic Review of Household and Family Alcohol Use and Childhood Neurodevelopmental Outcomes in Low- and Middle-Income Countries

Childhood exposure to alcohol misuse by household adults has been related to childhood developmental delay, cognitive impacts, mental illness, and problem behaviours. Most evidence comes from high income countries. This systematic review only included studies from low- and middle-income countries (LMICs). Five databases were searched from 1990-2020. Twenty-eight studies of children 0-12 years were included, with 42,599 participants from 11 LMICs. The most common outcome was behavioural problems/disorders (19 studies). Despite varying study designs, this review found that alcohol misuse by household members in LMICs is associated with adverse child neurodevelopmental outcomes, although casual inferences cannot be drawn in the absence of well conducted prospective studies. Statistically significant correlations were described between parental alcohol misuse and child emotional and behavioural difficulties, cognitive delay, and risky behaviours. In future, prospective cohort studies are recommended, with adjustment for confounders.

Elucidating the Links Between Mother and Father Alcohol Use Disorder and Adolescent Externalizing Psychopathology: A Test of Transmission Specificity Within Competing Factor Structures and Genetic and Environmental Liabilities

Parental alcohol use disorder (AUD) is a substantiated risk factor for adolescent externalizing psychopathology; however, the level of specificity at which risk from parental AUD is transmitted to adolescent offspring should be interrogated further. The current study modeled competing factor structures of psychopathology in a sample of 502 adolescent twin pairs (Mage = 13.24 years) and tested associations with mother and father AUD. The bifactor model exhibited the best fit to the data when contrasted with correlated factors and general factor models. Paternal AUD predicted the externalizing and internalizing correlated factors, the adolescent P-factor but not the residual externalizing and internalizing factors, and the general factor. No significant associations with maternal AUD were noted. Lastly, the latent factors of adolescent psychopathology were all moderately heritable (h2 = 0.44-0.59) and influenced by the nonshared environment. Shared genetic factors primarily explained externalizing and internalizing covariance. Findings suggest that efforts to mitigate risk in offspring of fathers exhibiting AUD require broader approaches that address the full range of adolescent symptomology.

Associations among bullying role behaviors and academic performance over the course of an academic year for boys and girls

Although some research has evidenced a negative association between involvement in bullying and academic performance, more work is needed to understand the associations between academic performance and involvement in a more comprehensive range of bully role behaviors. The goals of the current study were to determine (a) the associations among a broader range of bully role behaviors (i.e., bullying, assisting, victimization, defending, and outsider behavior) and academic performance (i.e., grade point average; GPA), and (b) gender differences within these associations. The current study investigated these issues over the course of an academic year with 7794 students in middle through high school. Bullying behaviors were assessed in the fall and GPA data were gathered from school records from the spring of the same academic year. The results identified significant negative associations between bullying (b = -0.07, p = .001), assisting (b = -0.16, p < .001), victimization (b = -0.06, p < .001), and defending (b = -0.04, p < .001) with student GPA, whereas no significant association emerged for outsider behavior and GPA (b = -0.02, p = .13). In addition, several gender differences were found in these associations, including a stronger negative association between assisting and GPA for girls (b = -0.23, p = .001) than for boys (b = -0.08, p = .014) and a significant negative association between victimization and GPA for girls (b = -0.09, p < .001), but not boys (b = -0.02, p = .117). Differences in results across schools were also examined in an exploratory manner. The educational impact associated with bullying behaviors, limitations of the current study, and suggestions for future research are discussed.

Tulve N. A Systematic Review and Meta-Analysis Investigating the Relationship between Exposures to Chemical and Non-Chemical Stressors during Prenatal Development and Childhood Externalizing Behaviors

Childhood behavioral outcomes have been linked to low quality intrauterine environments caused by prenatal exposures to both chemical and non-chemical stressors. The effect(s) from the many stressors a child can be prenatally exposed to may be influenced by complex interactive relationships that are just beginning to be understood. Chemical stressors influence behavioral outcomes by affecting the monoamine oxidase A (MAOA) enzyme, which is involved in serotonin metabolism and the neuroendocrine response to stress. Non-chemical stressors, particularly those associated with violence, have been shown to influence and exacerbate the externalizing behavioral outcomes associated with low MAOA activity and slowed serotonin metabolism. The adverse developmental effects associated with high stress and maternal drug use during pregnancy are well documented. However, research examining the combined effects of other non-chemical and chemical stressors on development and childhood outcomes as a result of gestational exposures is scarce but is an expanding field. In this systematic review, we examined the extant literature to explore the interrelationships between exposures to chemical and non-chemical stressors (specifically stressful/traumatic experiences), MAOA characteristics, and childhood externalizing behaviors. We observed that exposures to chemical stressors (recreational drugs and environmental chemicals) are significantly related to externalizing behavioral outcomes in children. We also observed that existing literature examining the interactions between MAOA characteristics, exposures to chemical stressors, and traumatic experiences and their effects on behavioral outcomes is sparse. We propose that maternal stress and cortisol fluctuations during pregnancy may be an avenue to link these concepts. We recommend that future studies investigating childhood behaviors include chemical and non-chemical stressors as well as children’s inherent genetic characteristics to gain a holistic understanding of the relationship between prenatal exposures and childhood behavioral outcomes.

Single nucleotide polymorphism heritability and differential patterns of genetic overlap between inattention and four neurocognitive factors in youth

Theoretical models of attention-deficit/hyperactivity disorder implicate neurocognitive dysfunction, yet neurocognitive functioning covers a range of abilities that may not all be linked with inattention. This study (a) investigated the single nucleotide polymorphism (SNP) heritability (h2SNP) of inattention and aspects of neurocognitive efficiency (memory, social cognition, executive function, and complex cognition) based on additive genome-wide effects; (b) examined if there were shared genetic effects among inattention and each aspect of neurocognitive efficiency; and (c) conducted an exploratory genome-wide association study to identify genetic regions associated with inattention. The sample included 3,563 participants of the Philadelphia Neurodevelopmental Cohort, a general population sample aged 8-21 years who completed the Penn Neurocognitive Battery. Data on inattention was obtained with the Kiddie Schedule of Affective Disorders (adapted). Genomic relatedness matrix restricted maximum likelihood was implemented in genome-wide complex trait analysis. Analyses revealed significant h2SNP for inattention (20%, SE = 0.08), social cognition (13%, SE = 0.08), memory (17%, SE = 0.08), executive function (25%, SE = 0.08), and complex cognition (24%, SE = 0.08). There was a positive genetic correlation (0.67, SE = 0.37) and a negative residual covariance (-0.23, SE = 0.06) between inattention and social cognition. No SNPs reached genome-wide significance for inattention. Results suggest specificity in genetic overlap among inattention and different aspects of neurocognitive efficiency.

Impact of autism-associated genetic variants in interaction with environmental factors on ADHD comorbidities: an exploratory pilot study

Attention-deficit/hyperactivity disorder (ADHD) is determined by genetic and environmental factors, and shares genetic risk with ASD. Functional single-nucleotide polymorphisms of the metabotropic glutamatergic signaling pathway are reported to increase the risk for ASD. The aim of this pilot study was to explore the main effects of respective ASD variants as well as their interaction effects with well-replicated ADHD environmental risk factors on the risk for ADHD, ADHD symptom severities, and comorbidities. We included 318 children with ADHD, aged 5-13 years, and their parents (N = 164 trios, N = 113 duos, N = 41 singletons). Interaction of ASD risk variants CYFIP1-rs7170637, CYFIP1-rs3693, CAMK4-rs25925, and GRM1-rs6923492 with prenatal biological and lifetime psychosocial risk factors was explored in a subsample with complete environmental risk factors (N = 139 trios, N = 83 duos, two singletons) by transmission disequilibrium test and stepwise regression analyses. We identified nominally significant (alpha < 0.05) GxE interactions of acute life events with CYFIP1-rs3693 on ADHD diagnosis (p = 0.004; fdr = 0.096) but no significant association of any single marker. Further results suggest that the risk for comorbid disruptive disorders was significantly modulated by GxE interactions between familial risk factors and CAMK4-rs25925 (p = 0.001; fdr = 0.018) and prenatal alcohol exposure with CYFIP1-rs3693 (p = 0.003; fdr = 0.027); both findings survived correction for multiple testing (fdr value < 0.05). Nominal significant GxE interactions moderating the risk for anxiety disorders have also been identified, but did not pass multiple testing corrections. This pilot study suggests that common ASD variants of the glutamatergic system interact with prenatal and lifetime psychosocial risk factors influencing the risk for ADHD common comorbidities and thus warrants replication in larger samples.

Prenatal alcohol exposure and offspring mental health: A systematic review

BACKGROUND

High levels of alcohol use in pregnancy have been shown to be associated with negative physical health consequences in offspring. However, the literature is less clear on the association of alcohol use in pregnancy and offspring mental health, specifically for low levels of prenatal alcohol exposure. We conducted a systematic review to evaluate studies examining this association.

METHODS

Studies were identified by searching PsycINFO, PubMed and Web of Science, and were included if they examined alcohol use during pregnancy as an exposure and offspring mental health at age 3 or older as an outcome. We excluded non-English language publications and studies of fetal alcohol syndrome.

RESULTS

Thirty-three studies were included and were categorized by mental health outcomes: anxiety/depression, emotional problems, total internalizing problems, total problem score, and conduct disorder. Over half of the analyses reported a positive association of prenatal alcohol exposure and offspring mental health problems.

CONCLUSIONS

Our review suggests that maternal alcohol use during pregnancy is associated with offspring mental health problems, even at low to moderate levels of alcohol use. Future investigation using methods that allow stronger causal inference is needed to further investigate if these associations shown are causal.

Genome-wide association study of alcohol use disorder identification test (AUDIT) scores in 20 328 research participants of European ancestry

Genetic factors contribute to the risk for developing alcohol use disorder (AUD). In collaboration with the genetics company 23andMe, Inc., we performed a genome-wide association study of the alcohol use disorder identification test (AUDIT), an instrument designed to screen for alcohol misuse over the past year. Our final sample consisted of 20 328 research participants of European ancestry (55.3% females; mean age = 53.8, SD = 16.1) who reported ever using alcohol. Our results showed that the 'chip-heritability' of AUDIT score, when treated as a continuous phenotype, was 12%. No loci reached genome-wide significance. The gene ADH1C, which has been previously implicated in AUD, was among our most significant associations (4.4 × 10-7 ; rs141973904). We also detected a suggestive association on chromosome 1 (2.1 × 10-7 ; rs182344113) near the gene KCNJ9, which has been implicated in mouse models of high ethanol drinking. Using linkage disequilibrium score regression, we identified positive genetic correlations between AUDIT score, high alcohol consumption and cigarette smoking. We also observed an unexpected positive genetic correlation between AUDIT and educational attainment and additional unexpected negative correlations with body mass index/obesity and attention-deficit/hyperactivity disorder. We conclude that conducting a genetic study using responses to an online questionnaire in a population not ascertained for AUD may represent a cost-effective strategy for elucidating aspects of the etiology of AUD.

Prenatal Alcohol Exposure and Child Psychosocial Behavior: A Sibling Fixed-Effects Analysis

Background: The association between low levels of alcohol consumption during pregnancy and children's health remains unclear because of the difficulty in ruling out residual genetic and environmental confounding factors. In this study, using a within-family sibling fixed effects design, we sought to examine the association between low prenatal alcohol exposures (PAE) and children's overall psychosocial behavior in a Japanese cohort. Methods: We used maternal and sibling data from the Japanese Study of Stratification, Health, Income and Neighborhood 2012-2013. Households were recruited from the Tokyo metropolitan area through clustered random sampling. Children under 18 years old who have siblings (n = 1,600) and their mothers were selected. PAE status was retrospectively measured, and classified by binominal and continuous measurements. Outcome measures of children's psychosocial behavior were assessed with the Child Behavior Checklist T-score. Results: Low PAE was significantly associated with the offspring's anxiety problems (β = 1.54, 95%CI = 0.26, 2.82) and internalizing problems (β = 2.73, 95%CI = 0.87, 4.60), and marginally significant with the offspring's total problem scores (β = 2.34, 95%CI = -0.24, 4.92). There was no significant difference in PAE between boys and girls when it comes to behavioral problems. Conclusions: Low PAE was associated with children's anxiety, internalizing problems and overall problems, taking into account possible unobserved genetic and environmental confounding influences.

Co-use of tobacco and marijuana during pregnancy: Pathways to externalizing behavior problems in early childhood

Use and co-use of tobacco and marijuana during pregnancy are associated with the development of social, cognitive, and behavioral problems for infants and children. However, less is known about the potential developmental impact of the use of tobacco and marijuana in tandem. The present study examined an etiological model for the development of externalizing behavior problems (EBP) in early childhood in a high risk sample (N = 247) of mother-infant dyads with prospective data from pregnancy to 36 months of child age. Co-use during pregnancy and continued maternal tobacco and marijuana use from infancy through early childhood were investigated. Although direct pathways from exposure during pregnancy to EBP were not significant, there was a significant indirect pathway from prenatal tobacco use to EBP via lower breastfeeding duration to lower maternal warmth/sensitivity to EBP, and a pathway from higher maternal affective dysregulation to higher EBP. These results highlight the importance of considering cascading effects of substance use during pregnancy on parental processes within the context of developmental risk and protection.

Externalizing Behavior Across Childhood as Reported by Parents and Teachers: A Partial Measurement Invariance Model

The externalizing spectrum may explain covariation among externalizing disorders observed in childhood and adulthood. Few prospective studies have examined whether externalizing spectrum might manifest differently across time, reporters, and gender during childhood. We used a multitrait, multimethod model with parent and teacher report of attention-deficit/hyperactivity disorder (ADHD) symptoms, oppositional defiant disorder (ODD) symptoms, and conduct disorder (CD)symptoms from kindergarten to Grade 5 in data from the Fast Track Project, a large multisite trial for children at risk for conduct problems ( n = 754). The externalizing spectrum was stably related to ADHD, ODD, and CD symptoms from kindergarten to Grade 5, with similar contributions from parents and teachers. Configural, metric, and scalar invariance were largely supported across time, suggesting that the structure of the externalizing spectrum is stable over time. Configural and partial metric invariance were supported across gender, but scalar invariance was not supported, with intercepts consistently higher for males than for females. Overall, our findings confirm other research that the externalizing spectrum can be observed early in development as covariation between ADHD, ODD, and CD, and extend that work to show that it is relatively consistent across time and reporter, but not consistent across gender.

Recent developments in the genetics of attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a developmental psychiatric disorder that affects children and adults. ADHD is one of the psychiatric disorders with the strongest genetic basis according to familial, twin, and single nucleotide polymorphisms (SNP)-based epidemiological studies. In this review, we provide an update of recent insights into the genetic basis of ADHD. We discuss recent progress from genome-wide association studies (GWAS) looking at common variants as well as rare copy number variations. New analysis of gene groups, so-called functional ontologies, provide some insight into the gene networks afflicted, pointing to the role of neurodevelopmentally expressed gene networks. Bioinformatic methods, such as functional enrichment analysis and protein-protein network analysis, are used to highlight biological processes of likely relevance to the etiology of ADHD. Additionally, copy number variations seem to map on important pathways implicated in synaptic signaling and neurodevelopment. While some candidate gene associations of, for example, neurotransmitter receptors and signaling, have been replicated, they do not seem to explain significant variance in recent GWAS. We discuss insights from recent case-control SNP-GWAS that have presented the first whole-genome significant SNP in ADHD.

Within-Family Effects of Smoking during Pregnancy on ADHD: the Importance of Phenotype

We sought to test within- and between- family associations of smoking during pregnancy (SDP) and attention deficit-hyperactivity disorder (ADHD) symptoms using a structured interview based on the conventional Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) symptoms and the Strengths and Weaknesses of ADHD-Symptoms and Normal-Behavior (SWAN) scale, which is a population based measure that grew out of the notion that an ADHD diagnosis exists on the extreme end of a continuum of normative behaviors and includes both above- and below- average performance on attention and activity. We used a sibling-comparison approach in a sample of 173 families including siblings aged 7-16 years (52% male) drawn from the state of Missouri, USA, wherein mothers smoked during one pregnancy but not the other. There was a within-family effect of smoking during pregnancy on SWAN hyperactivity/impulsivity and SWAN total ADHD behaviors. The associations between SDP and DSM-IV-based ADHD symptom dimensions as well as SWAN inattention were explained by familial confounds. These findings suggest that SDP exerts a potentially causal effect on increased ADHD hyperactive/impulsive behaviors and that this SDP effect is best captured when hyperactivity/impulsivity is assessed more normatively across the population, rather than specifically assessing problematic behaviors via DSM symptoms. Thus, any potentially causal effect of SDP on ADHD symptom dimensions may be restricted to hyperactive/impulsive behaviors rather than inattention, and normative, non-DSM-IV based behavioral measures may provide a more sensitive test of mechanisms of SDP-ADHD symptom associations, particularly in non-clinical samples.

Prenatal Exposure Effects on Early Adolescent Substance Use: Preliminary Evidence From a Genetically Informed Bayesian Approach

OBJECTIVE

Given the controversy surrounding the question of whether there are direct or causal effects of exposure to maternal smoking during pregnancy (SDP) on offspring outcomes such as substance use during the adolescent years, we sought to test, on a preliminary basis, within- and between-family associations of SDP and initiation of substance use early in adolescence (by age 15 years) using a discordant sibling design.

METHOD

We used a sibling-comparison approach in a sample of 173 families drawn from the state of Missouri, wherein mothers were discordant for smoking behaviors between two different pregnancies, to test for associations of SDP and initiation of substance use in a younger adolescent cohort. The discordant sibling comparison approach allows for disentangling familial effects from direct effects of SDP through the purposeful collection of data from siblings within the same family with differential exposure.

RESULTS

There were no between- or within-family effects of SDP on initiation of any type of substance use (alcohol, marijuana, smoking, and other drug classes), suggesting that SDP does not exert a direct effect on substance use in early adolescence.

CONCLUSIONS

Preliminary findings did not support an association of SDP and initiation of substance use in this younger adolescent sample. Studies such as this one can help build a body of evidence to explain whether associations of SDP and adolescent outcomes reflect a direct effect of SPD or may instead be attributable to familial confounders that are controlled in the discordant sibling design.

Cannabis Involvement and Nonsuicidal Self-Injury: A Discordant Twin Approach

OBJECTIVE

Cannabis use, particularly at an early age, has been linked to suicidal thoughts and behavior, but minimal work has examined the association between cannabis use and lifetime nonsuicidal self-injury (NSSI). The current study aims to characterize the overlap between lifetime and early cannabis use and NSSI and to examine genetic and environmental mechanisms of this association.

METHOD

Adult male and female twins from the Australian Twin Registry (N = 9,583) were used to examine the odds of NSSI associated with lifetime cannabis use and early cannabis use (i.e., <17 years of age). These associations were also examined within monozygotic (MZ) twins discordant for cannabis use and MZ twins discordant for early cannabis use. Analyses were replicated in an independent sample of female twins (n = 3,787) accounting for the age at onset of cannabis use and NSSI.

RESULTS

Lifetime cannabis use (odds ratio [OR] = 2.84, 95% CI [2.23, 3.61]) and early cannabis use were associated with increased odds of NSSI (OR = 2.15, 95% CI [1.75, 2.65]), and this association remained when accounting for covariates. The association was only significant, however, in MZ twin pairs discordant for early cannabis use (OR = 3.20, 95% CI [1.17, 8.73]). Replication analyses accounting for the temporal ordering of cannabis use and NSSI yielded similar findings of nominal significance.

CONCLUSIONS

Results suggest that NSSI is associated with cannabis involvement via differing mechanisms. For lifetime cannabis use, the lack of association in discordant pairs suggests the role of shared genes and family environment. However, in addition to such shared familial influences, person-specific and putatively causal factors contribute to the relationship between early cannabis use and NSSI. Therefore, delaying the onset of cannabis use may reduce exposure to influences that exacerbate vulnerabilities to NSSI.

Smoking during pregnancy and ADHD risk: A genetically informed, multiple-rater approach

Maternal smoking during pregnancy (SDP) is a significant public health concern with adverse consequences to the health and well-being of the developing child, including behavioral outcomes such as Attention-Deficit Hyperactivity Disorder (ADHD). There is substantial interest in understanding the nature of this reported association, particularly in light of more recent genetically informed studies that suggest that the SDP-ADHD link is less clear than once thought. In a sample of families (N = 173) specifically selected for sibling pairs discordant for prenatal smoking exposure, we use a sibling-comparison approach that controls for shared genetic and familial influences to assess the effects of SDP on ADHD symptom dimensions. ADHD was measured by both parent and teacher report on the Conners report forms and the Child Behavior Checklist/Teacher Report Form (CBCL/TRF). Results for the CBCL/TRF Total ADHD score are consistent with prior genetically informed approaches and suggest that previously reported associations between SDP and ADHD are largely due to familial confounding rather than causal teratogenic effects. However, results from the Conners parent report suggest a potentially causal effect of SDP on hyperactive/impulsive and, to a lesser extent, total ADHD symptoms; SDP results in increased parent-reported hyperactive/impulsive and total ADHD symptoms even after accounting for genetic and familial confounding factors. This suggests that the Conners assessment (parent-report) may provide a sensitive measure for use in studies examining child specific SDP effects on continuous and dimensional aspects of ADHD. © 2016 Wiley Periodicals, Inc.

Childhood attention-deficit/hyperactivity disorder symptoms and the development of adolescent alcohol problems: A prospective, population-based study of Swedish twins

Children with attention-deficit/hyperactivity disorder (ADHD) are at increased risk of problematic alcohol and other substance use in adolescence. This study used data from an ongoing, prospective, population-based twin study of Swedish children and adolescents to evaluate the extent to which the association between ADHD symptoms and alcohol problems reflects a unique source of genetic or environmental risk related to ADHD versus a broader predisposition to youth externalizing behavior. We used all available data from same-sex monozygotic (MZ) and dizygotic (DZ) twins on ADHD symptoms in childhood (age 9/12; N = 15,549) and alcohol problems in late adolescence (age 18; N = 2,564). Consistent with prior longitudinal studies, the phenotypic association between hyperactive/impulsive ADHD symptoms and alcohol problems was small in magnitude, whereas the association for inattentive symptoms was even weaker. Additive genetic influences explained 99.8% of the association between hyperactive/impulsive symptoms and alcohol problems. Furthermore, we found that the genetic risk specifically associated with hyperactive/impulsive symptoms was attenuated when estimated in the context of externalizing behavior liability during childhood, of which ADHD symptoms were specific expressions. In sensitivity analyses exploring hyperactivity in mid-adolescence, we found a similar pattern of genetic associations. These results are consistent with previous findings of genetically driven overlap in the etiology of ADHD and problematic alcohol use. At least some of this co-occurrence may result from a general predisposition to externalizing behaviors in youth. © 2015 Wiley Periodicals, Inc.

A Propensity Scoring Approach to Characterizing the Effects of Maternal Smoking During Pregnancy on Offspring's Initial Responses to Cigarettes and Alcohol

When examining the effects of prenatal exposure to maternal smoking during pregnancy (MSDP) on later offspring substance use, it is critical to consider familial environments confounded with MSDP. The purpose of this study was to examine the effect of MSDP on offspring's initial reactions to cigarettes and alcohol, which are indicators of future substance-use related problems. We tested these effects using two propensity score approaches (1) by controlling for confounding using the MSDP propensity score and (2) examining effects of MSDP across the MSDP risk distribution by grouping individuals into quantiles based on their MSDP propensity score. This study used data from 829 unrelated mothers with a reported lifetime history of smoking to determine the propensity for smoking only during their first trimester (MSDP-E) or throughout their entire pregnancy (MSDP-T). Propensity score analyses focused on the offspring (N = 1616 female twins) of a large subset of these mothers. We examined the effects of levels of MSDP-E/T on offspring initial reactions to their first experiences with alcohol and cigarettes, across the distribution of liability for MSDP-E/T. MSDP-E/T emerged as significant predictors of offspring reactions to alcohol and cigarettes, but the effects were confounded by the familial liability for MSDP. Further, the unique MSDP effects that emerged were not uniform across the MSDP familial risk distribution. Our findings underscore the importance of properly accounting for correlated familial risk factors when examining the effects of MSDP on substance related outcomes.

Effects of Maternal Smoking during Pregnancy on Offspring Externalizing Problems: Contextual Effects in a Sample of Female Twins

Studies of maternal smoking during pregnancy (MSDP) suggest increased risk for cognitive impairment and psychiatric outcomes. However, it is uncertain whether these associations are the direct result of MSDP or related to confounding familial variables associated with MSDP. The current study employed propensity score analysis to examine the effects of MSDP on offspring EXT using data from a large sample of 979 unrelated mothers. Logistic regression models were used to determine the propensity that the offspring of these mothers were likely to be exposed to MSDP [i.e., smoked during only the first trimester (MSDP-EARLY[E]) or smoked throughout their pregnancy (MSDP-THROUGHOUT[T])] given known familial confounders. Analyses focused on the effect of MSDP-E/T on the EXT behavior in offspring of these mothers (N = 1616) were conducted across the distribution of liability for MSDP-E/T and at different levels of risk for MSDP-E/T. MSDP-E/T was associated with offspring EXT problems, but the effects were partly confounded by the familial liability for MSDP. Further, the observed effects were not consistent across all levels of the MSDP risk distribution. These findings suggest a direct association between MSDP and offspring EXT behaviors, and that varied associations observed across studies may be the result of differences in the level of familial confounders that also have an effect on offspring EXT.

Maternal Smoking During Pregnancy and Offspring Birth Weight: A Genetically-Informed Approach Comparing Multiple Raters

Maternal smoking during pregnancy (SDP) is a significant public health concern with adverse consequences to the health and well-being of the fetus. There is considerable debate about the best method of assessing SDP, including birth/medical records, timeline follow-back approaches, multiple reporters, and biological verification (e.g., cotinine). This is particularly salient for genetically-informed approaches where it is not always possible or practical to do a prospective study starting during the prenatal period when concurrent biological specimen samples can be collected with ease. In a sample of families (N = 173) specifically selected for sibling pairs discordant for prenatal smoking exposure, we: (1) compare rates of agreement across different types of report-maternal report of SDP, paternal report of maternal SDP, and SDP contained on birth records from the Department of Vital Statistics; (2) examine whether SDP is predictive of birth weight outcomes using our best SDP report as identified via step (1); and (3) use a sibling-comparison approach that controls for genetic and familial influences that siblings share in order to assess the effects of SDP on birth weight. Results show high agreement between reporters and support the utility of retrospective report of SDP. Further, we replicate a causal association between SDP and birth weight, wherein SDP results in reduced birth weight even when accounting for genetic and familial confounding factors via a sibling comparison approach.

Predictors of alcohol-related negative consequences in adolescents: A systematic review of the literature and implications for future research

OBJECTIVE

To conduct a systematic review of the literature examining risk and protective factors of alcohol related negative consequences (ARNCs) among adolescents.

METHODS

We conducted a systematic search of original empirical articles published between January 1, 1990 and June 1, 2015. The qualitative synthesis was performed using the Theory of Triadic Influence as a framework.

RESULTS

Fifty-two studies were reviewed. Intrapersonal (e.g., personality traits, drinking motives and expectancies, depression), interpersonal (e.g., parental and peer alcohol use, violence exposure) and attitudinal factors (e.g., media exposure to alcohol, religiosity) influence ARNCs. Emerging evidence of new trends contributing to ARNCs include ready mixed alcohol drinks and childhood trauma and abuse.

CONCLUSIONS

Risk factors from all domains of influence were observed. More research is needed on protective factors and how alcohol use interacts with preventive factors in predicting ARNCs. The conceptualization of negative consequences varies significantly between studies and may impact the external validity of previous research.

Genetic and environmental contributions to the association between attention deficit hyperactivity disorder and alcohol dependence in adulthood: A large population-based twin study

Previous research indicates that attention deficit hyperactivity disorder (ADHD) frequently co-occurs with alcohol dependence; however, the extent to which shared genetic risk factors underpin this association remains unclear. The aim of this study is to investigate the relative importance of genetic, shared, and nonshared environmental factors for the overlap between ADHD and alcohol dependence in adults. Almost 18,000 adult twins aged 20-45 years, from more than 12,000 twin pairs (5,420 complete pairs), from the population-representative Swedish Twin Registry, were included. Self-ratings were used to assess symptoms of ADHD and alcohol dependence. Twin analysis was used to determine the role of additive genetic (A), shared (C), and nonshared environmental (E) factors. As a result, we found a significant association between ADHD and alcohol dependence (odds ratio 3.58; 95% confidence interval, 2.85-4.49). Twin analysis suggested that shared genetic risk factors explained 64% of the overlap between ADHD and alcohol dependence. Nonshared environmental factors accounted for the remaining 36%, whereas the contribution of shared environmental factors was minimal. We found no support for statistically significant sex differences in the overlap between ADHD and alcohol dependence. In conclusion the overlap between ADHD and alcohol dependence in adulthood was largely explained by shared genetic risk factors. This is an important step toward understanding the underlying nature of the risk of alcohol dependence in patients with ADHD and suggests that individuals with ADHD and their family members are important targets for alcohol prevention and treatment. © 2015 Wiley Periodicals, Inc.

ADHD symptoms, autistic traits, and substance use and misuse in adult Australian twins

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder frequently co-occur. Several studies show increased risk of substance use disorders in ADHD, yet there is limited information related to how ADHD symptoms, autistic traits, and their combined effects are associated with nicotine, alcohol, and cannabis use and use disorders in the general population.

METHOD

Cross-sectional interview and self-report questionnaire data from 3,080 young adult Australian twins (mean age 31.9 years) were used to assess ADHD symptoms, autistic traits, substance use, and substance use disorders. Substance use disorders-based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria-were assessed in the full sample as well as in those who reported substance use. Logistic regression analyses were used for comparing the associations between ADHD symptoms, autistic traits, substance use, and substance misuse after conduct disorder, sex, age, and zygosity were controlled for.

RESULTS

Greater ADHD symptoms and autistic traits scores were associated with elevated levels of regular smoking; cannabis use; and nicotine, alcohol, and cannabis use disorders, even after conduct disorder was adjusted for. In contrast, for alcohol use, those with high autistic traits scores were less likely to report drinking to intoxication. However, upon initiation, and similar to the findings for nicotine and cannabis, they were at elevated risk for developing alcohol dependence.

CONCLUSIONS

Increased liability to ADHD and elevated autistic traits scores were associated with substance use and misuse, with the exception of alcohol use. Given the social underpinnings of drinking, persons with autistic traits may be less likely to engage in it; however, upon engagement in drinking, their vulnerability to alcohol dependence is elevated.

Genetic influences on alcohol use across stages of development: GABRA2 and longitudinal trajectories of drunkenness from adolescence to young adulthood

Longitudinal analyses allow us to understand how genetic risk unfolds across development, in a way that is not possible with cross-sectional analyses of individuals at different ages. This has received little attention in genetic association analyses. In this study, we test for genetic effects of GABRA2, a gene previously associated with alcohol dependence, on trajectories of drunkenness from age 14 to 25. We use data from 1070 individuals who participated in the prospective sample of the Collaborative Study on the Genetics of Alcoholism, in order to better understand the unfolding of genetic risk across development. Piecewise linear growth models were fit to model the influence of genotype on rate of increase in drunkenness from early adolescence to young adulthood (14-18 years), the change in drunkenness during the transition to adulthood (18-19 years) and the rate of change in drunkenness across young adulthood (≥ 19 years). Variation in GABRA2 was associated with an increase in drunkenness that occurred at the transition between adolescence and adulthood. The genotypic effect was more pronounced in females. These analyses illustrate the importance of longitudinal data to characterize how genetic effects unfold across development. The findings suggest that transitions across important developmental periods may alter the relative importance of genetic effects on patterns of alcohol use. The findings also suggest the importance of considering gender when evaluating genetic effects on drinking patterns in males and females.

Genetic and environmental influences on the relationship between adult ADHD symptoms and self-reported problem drinking in 6024 Dutch twins

BACKGROUND

Cross-sectional and longitudinal studies have shown a positive association between attention deficit hyperactivity disorder (ADHD) and problematic alcohol use in adults. To what extent this association is explained by genetic and environmental factors is largely unknown.

METHOD

Data on ADHD and alcohol consumption were collected by self-report in 6024 adult Dutch twins. ADHD symptoms were assessed by three subscales of the Conners' Adult ADHD Rating Scales - Self-Report: Screening Version (CAARS-S:SV): inattentiveness, hyperactivity and the ADHD index (ADHD-I). Problem drinking was defined as at least two self-reported alcohol-related problems on the CAGE questionnaire. Structural equation modelling was applied to the bivariate twin data to estimate genetic and environmental influences.

RESULTS

Heritability of ADHD symptoms ranged between 32% and 40% and heritability of problem drinking was 50%. The positive correlation between ADHD symptoms and problem drinking was confirmed in this general population sample, with phenotypic correlations between 0.20 and 0.28 and genetic correlations between 0.39 and 0.50. Phenotypic correlations are primarily (61-100%) explained by genetic influences with non-shared environmental influences explaining the remaining covariance. No significant quantitative or qualitative gender differences in covariance structure were found.

CONCLUSIONS

This study convincingly shows that ADHD symptoms and problem drinking are moderately but significantly correlated in adults and that genetic correlations are primarily underlying this association. This suggests that early interventions are required to prevent adolescents with ADHD from developing problematic levels of alcohol use. Furthermore, clinicians who treat alcohol-dependent patients should be aware that the patient may have a co-morbid condition of ADHD; integrated interventions are required.

DSM-IV defined conduct disorder and oppositional defiant disorder: an investigation of shared liability in female twins

BACKGROUND

DSM-IV specifies a hierarchal diagnostic structure such that an oppositional defiant disorder (ODD) diagnosis is applied only if criteria are not met for conduct disorder (CD). Genetic studies of ODD and CD support a combination of shared genetic and environmental influences but largely ignore the imposed diagnostic structure.

METHOD

We examined whether ODD and CD share an underlying etiology while accounting for DSM-IV diagnostic specifications. Data from 1446 female twin pairs, aged 11-19 years, were fitted to two-stage models adhering to the DSM-IV diagnostic hierarchy.

RESULTS

The models suggested that DSM-IV ODD-CD covariation is attributed largely to shared genetic influences.

CONCLUSIONS

This is the first study, to our knowledge, to examine genetic and environmental overlap among these disorders while maintaining a DSM-IV hierarchical structure. The findings reflect primarily shared genetic influences and specific (i.e. uncorrelated) shared/familial environmental effects on these DSM-IV-defined behaviors. These results have implications for how best to define CD and ODD for future genetically informed analyses.

Alcohol consumption in men is influenced by qualitatively different genetic factors in adolescence and adulthood

BACKGROUND

Alcohol consumption is influenced by genetic factors. Previous studies have examined the heritability of alcohol consumption, or related phenotypes, from adolescence into adulthood, frequently finding that total heritability changes over time. However, it remains unclear whether the same genes underlie liability to alcohol consumption across development versus whether novel risk genes become important over time. Method A population-based study of adult male twins (n=1790) born in Virginia, USA, retrospectively reported on their average monthly alcohol consumption from early adolescence through adulthood. We used twin modeling methods to explore genetic and environmental influences on alcohol consumption over time.

RESULTS

One latent genetic factor accounted for the majority of the heritability in alcohol consumption during mid- to late adolescence, but its influence declined thereafter; from young adulthood forward, heritability was largely attributable to a second genetic factor. The total heritability of alcohol consumption increased from 0 at ages 12-14 years to 0.40 by ages 18-21 years. Shared environmental factors declined in influence over time.

CONCLUSIONS

The heritability of alcohol consumption over time is dynamic both quantitatively and qualitatively. These results have important implications for gene identification endeavors. Furthermore, these findings could inform efforts to elucidate developmentally dynamic behaviors, such as antisocial behavior.

Prospective effects of adolescent indicators of behavioral disinhibition on DSM-IV alcohol, tobacco, and illicit drug dependence in young adulthood

OBJECTIVE

To identify robust predictors of drug dependence.

METHODS

This longitudinal study included 2361 male and female twins from an ongoing longitudinal study at the Center for Antisocial Drug Dependence (CADD) at the University of Colorado Boulder and Denver campuses. Twins were recruited for the CADD project while they were between the ages of 12 and 18. Participants in the current study were on average approximately 15years of age during the first wave of assessment and approximately 20years of age at the second wave of assessment. The average time between assessments was five years. A structured interview was administered at each assessment to determine patterns of substance use and Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; Fourth Edition) attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), and drug dependence symptoms. Cloninger's Tridimensional Personality Questionnaire was also used to assess novelty seeking tendencies (NS). At the second wave of assessment, DSM-IV dependence symptoms were reassessed using the same interview. Path analyses were used to examine direct and indirect mechanisms linking psychopathology and drug outcomes.

RESULTS

Adolescent substance use, CD, and NS predicted young adult substance dependence, whereas the predictive effects of ADHD were few and inconsistent. Furthermore, CD and NS effects were partially mediated by adolescent substance use.

CONCLUSIONS

Adolescent conduct problems, novelty seeking, and drug use are important indices of future drug problems. The strongest predictor was novelty seeking.

Twin study of the relationship between adolescent attention-deficit/hyperactivity disorder and adult alcohol dependence

OBJECTIVE

Adolescent problem behaviors such as conduct disorder and attention-deficit/hyperactivity disorder (ADHD) are often associated with alcohol problems in adulthood, particularly alcohol dependence. This association is partly a result of shared genetic liability. However, it is unclear whether ADHD, or an ADHD subtype, shares genetic influences with alcohol dependence beyond those also shared by conduct disorder.

METHOD

We evaluated phenotypic associations between adolescent conduct disorder and ADHD phenotypes with adult alcohol dependence in a population-based sample of adult male twins (N = 1,774). We then assessed genetic and environmental relationships among phenotypes using structural equation modeling.

RESULTS

Individually, conduct disorder and each ADHD factor were associated with adult alcohol dependence. Results from twin modeling indicate that a genetic factor common to conduct disorder and ADHD also loads strongly onto alcohol dependence. Even after controlling for genetic factors shared with conduct disorder and other ADHD factors, the hyperactivity component of ADHD shared significant residual genetic influences with alcohol dependence.

CONCLUSIONS

Most of the genetically mediated association between adolescent ADHD and adult alcohol dependence is shared with conduct disorder, reflecting a generalized risk to externalizing behaviors. The significant residual genetic covariance between the ADHD factor hyperactivity/impulsivity and alcohol dependence implies that impulsive behaviors less destructive/harmful than those manifested by conduct disorder can be indicative of genetic risk for adult alcohol dependence. However, the ADHD factors inattention and forgetfulness are not uniquely predictive of genetic/environmental risk for alcohol dependence.

Effects of intoxicating free-choice alcohol consumption during adolescence on drinking and impulsivity during adulthood in selectively bred high-alcohol preferring mice

BACKGROUND

Abuse of alcohol during adolescence continues to be a problem, and it has been shown that earlier onset of drinking predicts increased alcohol abuse problems later in life. High levels of impulsivity have been demonstrated to be characteristic of alcoholics, and impulsivity has also been shown to predict later alcohol use in teenage subjects, showing that impulsivity may precede the development of alcohol use disorders. These experiments examined adolescent drinking in a high-drinking, relatively impulsive mouse population and assessed its effects on adult drinking and adult impulsivity.

METHODS

Experiment 1: Selectively bred high-alcohol preferring (HAPII) mice were given either alcohol (free-choice access) or water only for 2 weeks during middle adolescence or adulthood. All mice were given free-choice access to alcohol 30 days later, in adulthood. Experiment 2: Adolescent HAPII mice drank alcohol and water, or water alone, for 2 weeks, and were then trained to perform a delay discounting task as adults to measure impulsivity. In each experiment, effects of volitional ethanol (EtOH) consumption on later behavior were assessed. We expected adolescent alcohol exposure to increase subsequent drinking and impulsivity.

RESULTS

Mice consumed significant quantities of EtOH, reaching average blood ethanol concentrations (BECs) of 142 mg/dl (adolescent) or 154 mg/dl (adult) in Experiment 1. Adolescent mice in Experiment 2 reached an average of 108 mg/dl. Mice exposed to alcohol in either adolescence or adulthood showed a transient increase in EtOH consumption, but we observed no differences in impulsivity in adult mice as a function of whether mice drank alcohol during adolescence.

CONCLUSIONS

These findings indicate that HAPII mice drink intoxicating levels of alcohol during both adolescence and adulthood and that this volitional intake has long-term effects on subsequent drinking behavior. Nonetheless, this profound exposure to alcohol during adolescence does not increase impulsivity in adulthood, indicating that long-term changes in drinking are mediated by mechanisms other than impulsivity.

The role of conduct disorder in the association between ADHD and alcohol use (disorder). Results from the Netherlands Mental Health Survey and Incidence Study-2

BACKGROUND

Much is unclear about the association between attention-deficit/hyperactivity disorder (ADHD) and alcohol use (disorder). Research on this subject is hindered by the role of conduct disorder (CD). We investigate whether (1) childhood ADHD is associated with higher prevalence and earlier onset of alcohol initiation, regular alcohol use and alcohol use disorder (AUD) (2) CD mediates or modifies this association.

METHODS

Data were derived from the baseline assessment of the Netherlands Mental Health Survey and Incidence Study-2, a general population study. ADHD and CD were assessed among respondents aged 18-44 (n=3309). ADHD, CD, and alcohol use (disorder) were assessed using the Composite International Diagnostic Interview 3.0.

RESULTS

Lifetime prevalence was 2.9% for ADHD, 5.6% for CD, 94.3% for alcohol initiation, 85.7% for regular alcohol use and 19.0% for AUD; mean ages of onset were 6.7, 11.5, 14.8, 16.7 and 19.2 years, respectively. After correction for gender and age, ADHD was associated with a higher prevalence of all three stages of alcohol use, but not with earlier onset of these stages. The association between ADHD and prevalence of AUD was fully explained by a mediating role of CD. CD did not modify the associations between ADHD and prevalence and onset of alcohol use (disorder).

CONCLUSIONS

The mediating role of CD in the association between ADHD and AUD suggests a developmental pathway from ADHD to CD and subsequent AUD. Early interventions in children with ADHD may prevent CD and subsequent onset of AUD.

An exploration of the associations of pregnancy and perinatal features with cytokines and tryptophan/kynurenine metabolism in children with attention-deficit hyperactivity disorder (ADHD)

Intra-individual variability of the characteristics of children with attention-deficit hyperactivity (ADHD) may reflect compromised glial energy supply in the synapse. We reported recently that while serum levels of a glial marker, the cytokine S100B, were not seriously altered, levels of other cytokines and tryptophan metabolites were related to symptoms, attention and variability. Here, we explore with a regression analysis whether levels of these substances were associated with features of the index pregnancy of potential aetiological significance. Serum was taken from 35 children with DSM-IV ADHD (14 on medication) and 21 typically developing controls to measure 8 cytokines (S100B, IL-2, IL-6, IL-10, IL-13, IL-16, TNF-α and IFN-γ) and 5 metabolites (Tryptophan, Kynurenine, Kynurenate [KA], 3-hydroxy-kynurenine [3HK] and 5-hydroxyindole acetic acid [5-HIAA]). The mothers received a 124-item questionnaire on features surrounding the pregnancy. (1) For children with ADHD, a shorter pregnancy and smaller birth weight were associated statistically with increased 3HK and IFN-γ and for obstetric problems with decreased TNF-α levels. (2) Maternal smoking related to decreasing kynurenine and increasing 3HK and S100B levels in ADHD children. Paternal smoking was associated with increased tryptophan in the controls and increased IL-6 levels in ADHD children. (3) The taking of supplements often related to decreasing TNF-α, increasing IL-10 and lower 5-HIAA levels in the ADHD children. Less 5-HIAA but more tryptophan was associated with earlier and later life events, respectively. (4) Increased IL-16 and 5-HIAA levels in the ADHD group related to reports of poorer infant health. Unexpectedly, more child care (seafood and time together) in ADHD than healthy families was implicated by lower tryptophan levels and an altered balance of pro-inflammatory cytokines. Across measures control families generally showed either non-significant associations or the opposite to those of the ADHD group. In ADHD children more than controls, the balance of potentially toxic or protective kynurenine metabolites and of pro- over anti-inflammatory cytokines may reflect the perinatal experience associated with stress, but not with maternal illness.

Harsh physical punishment as a specific childhood adversity linked to adult drinking consequences: evidence from China

AIMS

The aim of the current study is to estimate the association between childhood physical punishment (CPP) and level of alcohol use disorder (AUD), using two different approaches to take other childhood adversities into account.

DESIGN AND SETTING

Population survey using face-to-face interviews to a representative sample of non-institutionalized adult residents of Beijing and Shanghai, China.

PARTICIPANTS

A total of 5201 participants aged 18-70 years.

MEASUREMENTS

A version of the World Mental Health Composite International Diagnostic Interview was used. Standardized assessments covered early life experiences of childhood physical punishment, other childhood adversities, parental drinking problems, childhood conduct problems and clinical features of AUD.

FINDINGS

A robust association linking CPP and level of AUD was found, holding other childhood adversities constant (probit coefficient = 0.70, 95% CI = 0.40, 1.00) via covariate terms in structural equations modeling. Furthermore, there was evidence that CPP might exert an additional influence on level of AUD over and above a generally noxious family environment (probit coefficient = 0.20, 95% CI = 0.02, 0.38).

CONCLUSIONS

There appears to be a robust association between reports of harsh punishment in childhood and alcohol dependence in adulthood adjusting for a range of possible confounding factors. Whether the association is causal or whether both are related to a common underlying factor or recall bias needs to be investigated further.

Limited associations of dopamine system genes with alcohol dependence and related traits in the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD)

BACKGROUND

Over 50 years of evidence from research has established that the central dopaminergic reward pathway is likely involved in alcohol dependence (AD). Additional evidence supports a role for dopamine (DA) in other disinhibitory psychopathology, which is often comorbid with AD. Family and twin studies demonstrate that a common genetic component accounts for most of the genetic variance in these traits. Thus, DA-related genes represent putative candidates for the genetic risk that underlies not only AD but also behavioral disinhibition. Many linkage and association studies have examined these relationships with inconsistent results, possibly because of low power, poor marker coverage, and/or an inappropriate correction for multiple testing.

METHODS

We conducted an association study on the products encoded by 10 DA-related genes (DRD1-D5, SLC18A2, SLC6A3, DDC, TH, COMT) using a large, ethnically homogeneous sample with severe AD (n = 545) and screened controls (n = 509). We collected genotypes from linkage disequilibrium (LD)-tagging single nucleotide polymorphisms (SNPs) and employed a gene-based method of correction. We tested for association with AD diagnosis in cases and controls and with a variety of alcohol-related traits (including age-at-onset, initial sensitivity, tolerance, maximum daily drinks, and a withdrawal factor score), disinhibitory symptoms, and a disinhibitory factor score in cases only. A total of 135 SNPs were genotyped using the Illumina GoldenGate and Taqman Assays-on-Demand protocols.

RESULTS

Of the 101 SNPs entered into standard analysis, 6 independent SNPs from 5 DA genes were associated with AD or a quantitative alcohol-related trait. Two SNPs across 2 genes were associated with a disinhibitory symptom count, while 1 SNP in DRD5 was positive for association with the general disinhibitory factor score.

CONCLUSIONS

Our study provides evidence of modest associations between a small number of DA-related genes and AD as well as a range of alcohol-related traits and measures of behavioral disinhibition. While we did conduct gene-based correction for multiple testing, we did not correct for multiple traits because the traits are correlated. However, false-positive findings remain possible, so our results must be interpreted with caution.

Gender differences in the relationship of internalizing and externalizing psychopathology to alcohol dependence: likelihood, expression and course

OBJECTIVE

To determine whether internalizing and externalizing psychopathology were differentially associated with alcohol dependence in men and women.

METHODS

Four categories of lifetime psychopathology were examined: neither internalizing nor externalizing (NINE), internalizing only (IO), externalizing only (EO) and both internalizing and externalizing (BIE). Multivariate models assessed gender differences in the adjusted associations of these categories with the odds of lifetime alcohol dependence in a representative sample of 43,093 U.S. adults 18 and older and with clinical course and expression in a subsample of 4781 lifetime alcoholics.

RESULTS

The excess odds of lifetime alcohol dependence associated with IO, EO and BIE were significantly greater for women than men, OR=2.6, 8.8 and 10.7 versus 1.9, 4.0 and 6.5, respectively. Regardless of gender, the ORs were significantly higher for EO than IO and for BIE than EO. Gender differences in the expression and course of alcoholism were most pronounced for the categories of NINE and IO, with men having greater consumption, dependence severity and treatment but less familial alcoholism. Gender variation in the association of psychopathology with the expression and course of alcoholism was most evident in the BIE category, where the associations were stronger for women. Lifetime externalizing psychopathology was associated with an increased likelihood of treatment utilization, especially among women.

CONCLUSIONS

Findings highlight the need to increase alcoholism screening, prevention and intervention among women with psychopathology, especially externalizing. The greater numbers of internalizing than externalizing alcoholics emphasize the need to treat symptoms of depression and anxiety in alcohol treatment settings.

Do candidate genes discriminate patients with an autism spectrum disorder from those with attention deficit/hyperactivity disorder and is there an effect of lifetime substance use disorders?

OBJECTIVE

Autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD) are developmental disorders that overlap in a number of domains, sometimes complicating clinical distinction between both disorders. Although there is some evidence for a genetic overlap, there are no reports on genes that could differentiate between ASD and ADHD. Furthermore, it is not known whether this genetic overlap is influenced by co-morbid substance use disorders (SUD).

METHODS

A total of 110 adult patients with ASD (n=61) or ADHD (n=49) with or without a lifetime history of SUD participated in a study in which we genotyped polymorphisms in five known candidate genes for (one of) the disorders, i.e. the 5HTTLPR in SLC6A4/5-HTT, rs1800497 (TaqIA C>T) in DRD2, rs7794745 in CNTNAP2, rs1843809 in TPH2, and rs6565113 in CDH13. Genotyping was by Taqman-based analysis or by simple sequence length analysis, where appropriate.

RESULTS

ASD could be differentiated from ADHD with nominal statistical significance by the 5HTTLPR, and the polymorphisms in TPH2 and CNTNAP2. The results were independent of lifetime SUD status.

CONCLUSIONS

Serotonergic genes could prove to play an important role in differentiating between ASD and ADHD, but the results of this exploratory study need replication.

Associations of the DRD2 TaqIA polymorphism with impulsivity and substance use: preliminary results from a clinical sample of adolescents

BACKGROUND

The A1 allele of the TaqIA polymorphism (rs1800497) in the dopamine D2 receptor gene (DRD2) has been associated with substance use. It is unclear whether this allele is a marker for an underlying propensity for specifically developing a substance use disorder, or more generally to developing an externalizing psychiatric disorder highly correlated with substance use. It is also possible that DRD2 is related to a behavioral phenotype common to externalizing disorders and substance use.

METHOD

Data was obtained from 104 psychiatrically hospitalized adolescents in a larger assessment study. Adolescents were genotyped for the DRD2 TaqIA site, grouped as carriers of the A1 allele (A1+) or homozygous for the A2 allelle (A1-). Associations of the presence of the A1 allele with externalizing disorders, the intermediate phenotype of impulsivity, and measures of alcohol and drug use were examined.

RESULTS

A diagnosis of conduct disorder and impulsive behavior were both associated with severity of problem drinking and/or drug use. Further, interaction effects were found between the DRD2 TaqIA polymorphism and conduct disorder (trend level) as well as A1+ status and impulsivity, such that adolescents who were carriers of the A1 allele, and had conduct disorder or impulsive behavior, reported higher levels of problematic alcohol use than those who were non-carriers (A2/A2 or A1-). The same interaction effect between this polymorphism and impulsivity was found for severity of problem drug use. In contrast, no interaction effects were found between the DRD2 allele status and ADHD on severity of problem drinking or drug use.

DISCUSSION

These results suggest that the well documented relationship between conduct disorder, the behavioral phenotype of impulsivity, and problematic alcohol/drug use among adolescents may be moderated by A1 carrier status of the DRD2 gene.