Multiple mechanisms influencing the relationship between alcohol consumption and peer alcohol use

Hazardous alcohol use and alcohol-related harm in rural and remote communities: a scoping review

Alcohol use is a major risk factor for death and disease worldwide and alcohol-related harms appear to be more prevalent in rural and remote, relative to urban, communities. This Review synthesised international research on rural-urban disparities in hazardous and harmful alcohol use and risk factors for these outcomes within rural and remote communities. 280 studies from 49 countries were included in the Scoping Review. Most studies (60%) found rural, relative to urban, residence to be associated with an increased likelihood of hazardous alcohol use or alcohol-related harm. This proportion increased between 1990 and 2019 and varied by country, age group, and outcome type, being highest in Australia, among young adults, and for more severe alcohol-related harms, such as drink driving and alcohol-related suicide. Improved public health strategies to reduce the burden of alcohol use in rural communities are required but their efficacy will depend on how well they are tailored to the unique needs of the region they are implemented in.

Predicting Alcohol Dependence Symptoms by Young Adulthood: A Co-Twin Comparisons Study

Co-twin comparisons address familial confounding by controlling for genetic and environmental influences that twin siblings share. We applied the co-twin comparison design to investigate associations of adolescent factors with alcohol dependence (AD) symptoms. Participants were 1286 individuals (581 complete twin pairs; 42% monozygotic; and 54% female) from the FinnTwin12 study. Predictors included adolescent academic achievement, substance use, externalizing problems, internalizing problems, executive functioning, peer environment, physical health, relationship with parents, alcohol expectancies, life events, and pubertal development. The outcome was lifetime AD clinical criterion count, as measured in young adulthood. We examined associations of each adolescent domain with AD symptoms in individual-level and co-twin comparison analyses. In individual-level analyses, adolescents with higher levels of substance use, teacher-reported externalizing problems at age 12, externalizing problems at age 14, self- and co-twin-reported internalizing problems, peer deviance, and perceived difficulty of life events reported more symptoms of AD in young adulthood (ps < .044). Conversely, individuals with higher academic achievement, social adjustment, self-rated health, and parent-child relationship quality met fewer AD clinical criteria (ps < .024). Associations between adolescent substance use, teacher-reported externalizing problems, co-twin-reported internalizing problems, peer deviance, self-rated health, and AD symptoms were of a similar magnitude in co-twin comparisons. We replicated many well-known adolescent correlates of later alcohol problems, including academic achievement, substance use, externalizing and internalizing problems, self-rated health, and features of the peer environment and parent-child relationship. Furthermore, we demonstrate the utility of co-twin comparisons for understanding pathways to AD. Effect sizes corresponding to the associations between adolescent substance use, teacher-reported externalizing problems, co-twin-reported internalizing problems, peer deviance, and self-rated health were not significantly attenuated (p value threshold = .05) after controlling for genetic and environmental influences that twin siblings share, highlighting these factors as candidates for further research.

Maternal Parenting Behaviors Amplify Environmental Influences on Developmental Trajectories of Alcohol Use During Adolescence

Compared to peer alcohol use, less is known on how parenting practices may modify genetic and environmental contributions to alcohol use longitudinally across adolescence. This study examined whether two maternal parenting behaviors, supervision and harsh parenting, may suppress or amplify genetic and environmental influences on three distinct developmental trajectories of adolescent alcohol use: normative increasing, early-onset, and low trajectories. Participants were drawn from a longitudinal study of a population-based twin sample (N = 842, 84% European descent, 52.7% female). Adolescents self-reported their past year alcohol use at ages 13, 14, 15, and 17 years, and their mothers reported their supervision and harsh parenting when twins were 13, 15, and 17 years old. Maternal supervision amplified non-shared environmental influence on the normative increasing and early-onset trajectories, whereas maternal harsh parenting amplified shared environmental influence on the early-onset trajectory and non-shared environmental influence on the low trajectory, respectively. The findings suggest maternal parenting practices as a potent developmental context that modulates the environmental influences of other proximal processes on adolescent alcohol use, and suggest that family-based parenting-focused intervention could be especially beneficial for adolescents following the early-onset trajectory.

Co-development of alcohol use problems and antisocial peer affiliation from ages 11 to 34: selection, socialization and genetic and environmental influences

BACKGROUND AND AIMS

Social context is an important factor in determining the developmental trajectory of alcohol use. We examined the co-development between alcohol use problems and antisocial peer affiliation. We also estimated the genetic and environmental influences on alcohol use problems, antisocial peer affiliation and their co-development over time.

DESIGN

Longitudinal study using bivariate latent basis models with structured residuals (LBM-SR). A biometric model was then fitted to estimate the genetic and environmental influences on the growth factors and their covariances.

SETTING

The United States mid-west region.

PARTICIPANTS

Members of the Minnesota Twin Family Study (MTFS), an ongoing, longitudinal study of 3762 (52% female) twins (1881 pairs).

MEASUREMENTS

Alcohol use problems were assessed using a composite measure of average number of drinks per occasion in the past 12 months, maximum number of drinks in 24 hours and DSM-III-R symptoms of alcohol abuse and dependence. Antisocial peer affiliation was measured by self-report of the proportion of one's friends who exhibited types of antisocial behaviors.

FINDINGS

The LBM-SR model revealed that there was a large correlation between the growth factors for alcohol use problems and antisocial peer affiliation [r = 0.78, 95% confidence interval (CI) = 0.76, 0.80] and cross-lagged effects consistent with both selection and socialization effects. Additionally, antisocial peer affiliation in adolescence was associated with greater increases in alcohol use problems over time (r = 0.57, 95% CI = 0.54, 0.60). Genetic influences largely accounted for the association between antisocial peer affiliation in pre-adolescence and growth in alcohol use problems, while shared environmental influences accounted for the correlation between antisocial peer affiliation and alcohol use problems growth factors.

CONCLUSIONS

Antisocial peer affiliation in adolescence appears to be a salient, genetically influenced risk factor for early alcohol use and increase in alcohol use from adolescence to young adulthood.

A review of psychosocial factors linked to adolescent substance use

PURPOSE

Informed by ecological theories and models of influence, this review discusses various psychosocial risk and protective factors that contribute to adolescent substance use behavior. Given typical patterns of substance use initiation during this developmental period, an emphasis is placed on alcohol, cigarette, and marijuana use.

FINDINGS

Consistent with bioecological theories, peers and parents tend to have the strongest effect on adolescent substance use behavior. Influences can be both direct, such as offers and availability to use substances, as well as indirect influences, such as the perception of substance use approval. Schools and neighborhoods also contribute to adolescent substance use behavior, but this effect is often less direct. Moreover, the effect of neighborhoods on adolescent behavior reflects both structural components (e.g., neighborhood racial composition, teacher-student ratios) in addition to social process (e.g., neighborhood social cohesion, school connectedness). A review of parallel studies conducted with animals is also provided.

SUMMARY

Adolescent substance use behavior does not occur in a vacuum. Investigations must encompass the relevant social ecologies that affect adolescent behavior, including family, peer, school, and neighborhood contexts to provide a more complete understanding of substance use etiology.

Selective alterations in endogenous opioid system genes expression in rats selected for high ethanol intake during adolescence

Historically, the roots of alcoholism have been linked to either environment or heredity. However, the interaction between these factors is still largely unexplored. The evidence supports a link between alcohol consumption and the endogenous opioid system. We here studied the opioid genes expression in male and female Wistar rats derived from a short-term breeding program which selected -- at adolescence -- for high (ADHI line) or low (ADLO line) ethanol drinking. Specifically, in this work we analyzed central opioid gene expression in the rats of the second filial generation (S₂-ADLO and S₂-ADHI). Selective downregulation of pronociceptin (Pnoc) and its receptor (Oprl1) mRNA levels were observed in the prefrontal cortex of male S₂-ADHI rats when compared to S₂-ADLO, and for Oprl1 also in the nucleus accumbens. An increase in gene expression was instead observed for pro-opiomelanocortin (Pomc) in the nucleus accumbens of S₂-ADHI males when compared to S₂-ADLO, as well as for mu opioid receptor (Oprm1) but in females. The differences in mRNA levels may be due to the different alcohol consumption between the two groups of rats or may represent pre-existing differences between them. Moreover, we show a sex-specific modulation of the expression of these genes, thus pointing out the importance of sex on ethanol responses. The results might lead to more specific and effective pharmacological treatments for alcoholism.

Which adolescent factors predict alcohol misuse in young adulthood? A co-twin comparisons study

BACKGROUND AND AIMS

Research on adolescent predictors of later alcohol misuse is typically conducted on samples of singletons, and associations may be confounded by between-family differences. To address potential confounding, we applied a co-twin comparison design to evaluate whether differences between co-twins in a wide array of adolescent risk factors predicted differences in young adult alcohol misuse.

DESIGN

Longitudinal study in which associations between characteristics of the sample as adolescents were used to predict young adult alcohol misuse in individual-level analyses and co-twin comparisons.

SETTING

Finland.

PARTICIPANTS

A total of 3402 individuals (1435 complete twin pairs; 36% monozygotic; 57% female) from the FinnTwin12 study.

MEASUREMENTS

The young adult alcohol misuse outcome was a composite score of alcohol use and intoxication frequency. Adolescent predictors included factor scores representing academic performance, substance use, externalizing problems, internalizing problems, peer environment, physical health and relationship with parents; and single measures tapping alcohol expectancies, life events and pubertal development.

FINDINGS

In individual-level analyses, individuals with higher adolescent substance use, externalizing problems, time with friends, peer deviance, sports involvement, sleeping difficulties, parental discipline, positive alcohol expectancies and difficulty of life events reported higher alcohol misuse in young adulthood (Ps < 0.019, R²  = 0.0003-0.0310%). Conversely, those with higher adolescent internalizing problems, parent-child relationship quality and time with parents reported lower alcohol misuse (Ps < 0021, R²  = 0.0018-0.0093%). The associations with adolescent substance use and alcohol expectancies remained significant in co-twin comparisons (Ps < 0.049, R²  = 0.0019-0.0314%). Further, academic performance emerged as a significant predictor, such that individuals with higher grades compared with their co-twin reported higher young adult alcohol misuse (Ps < 0.029, R²  = 0.0449-0.0533%).

CONCLUSIONS

Adolescent substance use, positive alcohol expectancies and higher academic performance appear to be robust predictors of later alcohol misuse.

Contexts of alcohol use: A latent class analysis among Argentinean college students

BACKGROUND

Alcohol use, and the association between alcohol-related variables and drinking outcomes, seem to be context dependent. We employed Latent Class Analysis, a person-centered approach, to identify distinct subpopulations based on contexts of alcohol use. We also examined if the resulting classes differ in a set of alcohol-related variables that hold promise as potential targets of interventions.

METHOD

Argentinean college students N = 1083; 64 % women; M age = 19.73 ± 3.95) completed an online survey that assessed alcohol outcomes and related variables [motives for substance use, protective behavioral strategies (PBS) and normative perceptions of alcohol use].

RESULTS

Latent Class Analysis identified a 4-classes model for drinking contexts. These classes showed differential patterns of alcohol use (both in terms of frequency and quantity) and also differed in alcohol-related variables. Alcohol use was more prevalent in contexts characterized by the presence of peers, particularly the closest friend, small same-sex or coed groups. Close to 50 % of the sample reported drinking with family members. Students with a high probability of engaging in pregaming and nightclub drinking tend to use more PBS to control how much alcohol is consumed than those who do not drink in these contexts. All the classes significantly differed in their social reasons for drinking and in the number of alcohol-related negative consequences.

CONCLUSIONS

Our findings revealed subpopulations of college students that are heterogeneous regarding contexts of alcohol use, patterns of use and in a number of relevant variables. These distinctive subpopulations require different targeted interventions.

Peer Alcohol Use Differentially Amplifies Genetic and Environmental Effects on Different Developmental Trajectories of Adolescent Alcohol Use

PURPOSE

The purpose of the study was to investigate how peer alcohol use moderates genetic and environmental influences on three different developmental trajectories of alcohol use during adolescence: low (continuously low levels of use), early-onset fast-escalating (initiated use early, the level of use increased quickly), and normative increasing (started at a low level and increased steadily) using biometric modeling.

METHODS

Data were from a longitudinal study on a sample of population-based adolescent twins (N = 842, 52.7% female, 84% European Caucasian). Adolescents self-reported past-year alcohol use at age 13, 14, 15, and 17 years. Adolescents' nominated friends reported their own past-year alcohol use at age 13, 15, and 17 years.

RESULTS

Genetic and environmental influences on adolescents' alcohol use trajectories were differentially moderated by friends' alcohol use in different trajectories. Gene-environment interaction was implicated in the low and early-onset trajectories, such that genetic contributions were amplified when friends used more alcohol. Environment-environment interaction was involved in the normative increasing and early-onset trajectories, such that person-specific environmental contributions were amplified when friends' alcohol use increased.

CONCLUSIONS

Adolescent alcohol use remains a major public health issue, with peer alcohol use being a major risk factor. These findings suggest that close supervision to reduce deviant peer affiliation as well as preventions targeting peer group norms of alcohol use might be especially beneficial for adolescents following the normative increasing and early-onset trajectories.

Genetic and environmental influences on developmental trajectories of adolescent alcohol use

Adolescent alcohol use demonstrates distinct developmental trajectories with different times of onset, levels, and rates of growth. Twin research on adolescent alcohol use has shown that genetic influences are consistent with a gradual growth of risks, whereas non-shared environmental influences are more consistent with an accumulation of risks over time. The current study investigated the relative contributions of genetic and environmental influences on shaping different developmental trajectories of alcohol use through adolescence. Self-reported past year alcohol use was collected from 877 Canadian twins (47.1% males) at age 13, 14, 15, and 17 years. Growth mixture models were fit to examine different developmental trajectories of alcohol use, and biometric liability threshold models were fit to investigate genetic and environmental influences on the liability of belonging to identified trajectories. Three trajectories were identified: low (15.1%), early onset (8.2%), and normative increasing (76.7%). Memberships in the low and early-onset group were under genetic (27.6% and 34.7%), shared (42.4% and 21.5%), and non-shared environment influences (30.0% and 43.8%). Membership in the normative increasing group was under genetic (37.7%) and non-shared environment influences (62.3%). Non-shared environmental influences were significantly larger for the normative increasing trajectory than for the low trajectory. These findings provide a more refined picture of genetic and environmental influences in the development of alcohol use in subgroups of adolescents. Genetic and environmental influences both matter, but to different degrees in different trajectories. Future research should identify specific shared and non-shared environmental experiences that distinguish different trajectories.

A Multilevel Study of Alcohol Consumption in Young Adults: Self-Efficacy, Peers' Motivations and Protective Strategies

In both developing and underdeveloped countries there has been a worrying increase in the number of young people drinking alcohol; this public health problem warrants more research. This multilevel study analyzed the influence of drinking refusal self-efficacy, peers’ motivation, and protective behavioral strategies as predictors of alcohol consumption in a sample of 261 young people arranged into 52 social groups (peers who regularly shared leisure activities). A series of questionnaires were administered individually to evaluate beliefs and behaviors related to alcohol consumption at both individual level (drinking refusal self-efficacy) and peer level (enhancement motivation and protective behavioral strategies). The results showed that the individual variable (drinking refusal self-efficacy) predicted alcohol consumption behaviors. The multilevel design allowed us to evaluate the direct and moderated effects of peers’ enhancement motivation and protective behavioral strategies on the relationship between self-efficacy and drinking behavior. These results show the importance of developing cognitive, behavioral, and educational intervention programs to increase young people and university students’ confidence and ability to use protective strategies, in order to reduce alcohol use.

Friend Selection and Influence Effects for First Heavy Drinking Episode in Adolescence

OBJECTIVE

Heavy alcohol consumption has both immediate and longer-term risks for adolescents. Using a dynamic network modeling approach, this study investigated the role of adult supervision and affiliation with heavy drinking friends in predicting the risk of a first heavy drinking episode in a community sample of adolescents.

METHOD

Two cohorts of ninth grade youth (n = 1,220, 48% male) from seven communities were surveyed three times over the course of the school year (fall, winter, and spring), each time assessing their friendship networks, whether they had ever experienced a heavy drinking episode, frequency of heavy drinking over the past month, and the amount of unsupervised time spent with each of their friends over the past month.

RESULTS

Participants were more likely to form friendships with classmates with similar recent heavy drinking behavior, but similarity on adult supervision of time spent with friends had no effect on friendship selection. A negative interaction was observed between these two similarity effects, implying that they were antisynergistic. Risk for a first heavy drinking episode was greater for youth with friends who had experienced such an episode already. This effect was no stronger if these friends had more such episodes in the previous 30 days but was marginally stronger if the friends reported less adult supervision.

CONCLUSIONS

Heavy drinking-related friendships increase the risk of a first heavy drinking episode. Adult supervision of time spent with friends may reduce this risk. Results support interventions that target the spread of heavy drinking through adolescent social ecosystems, in addition to targeting the most at-risk individuals.

Exploring the relationship between polygenic risk for cannabis use, peer cannabis use and the longitudinal course of cannabis involvement

BACKGROUND AND AIMS

Few studies have explored how polygenic propensity to cannabis use unfolds across development, and no studies have yet examined this question in the context of environmental contributions such as peer cannabis use. Outlining the factors that contribute to progression from cannabis initiation to problem use over time may ultimately provide insights into mechanisms for targeted interventions. We sought to examine the relationships between polygenic liability for cannabis use, cannabis use trajectories from ages 12-30 years and perceived peer cannabis use at ages 12-17 years.

DESIGN

Mixed-effect logistic and linear regressions were used to examine associations between polygenic risk scores, cannabis use trajectory membership and perceived peer cannabis use.

SETTING

United States.

PARTICIPANTS

From the Collaborative Study on the Genetics of Alcoholism (COGA) study, a cohort of 1167 individuals aged 12-26 years at their baseline (i.e. first) interview.

MEASUREMENTS

Key measurements included life-time cannabis use (yes/no), frequency of past 12-month cannabis use, maximum life-time frequency of cannabis use, cannabis use disorder (using DSM-5 criteria) and perceived peer cannabis use. Polygenic risk scores (PRS) were created using summary statistics from a large (n = 162 082) genome-wide association study (GWAS) of cannabis use.

FINDINGS

Three trajectories reflecting no/low (n = 844), moderate (n = 137) and high (n = 186) use were identified. PRS were significantly associated with trajectory membership [P = 0.002-0.006, maximum conditional R2  = 1.4%, odds ratios (ORs) = 1.40-1.49]. Individuals who reported that most/all of their best friends used cannabis had significantly higher PRS than those who reported that none of their friends were users [OR = 1.35, 95% confidence interval (CI) = 1.04, 1.75, P = 0.023]. Perceived peer use itself explained up to 11.3% of the variance in trajectory class membership (OR = 1.50-4.65). When peer cannabis use and the cannabis use PRS were entered into the model simultaneously, both the PRS and peer use continued to be significantly associated with class membership (P < 0.01).

CONCLUSIONS

Genetic propensity to cannabis use derived from heterogeneous samples appears to correlate with longitudinal increases in cannabis use frequency in young adults.

Contribution of the Five Factors of Personality and Peers on Adolescent Alcohol Use: A Cross-National Study

Personality characteristics such as extraversion, low agreeableness and low conscientiousness are relevant for alcohol use during adolescence. In addition, having friends who use alcohol is one of the strongest predictors of adolescent alcohol consumption and its negative outcomes. The selection model posits that friends display similar alcohol consumption when their friendships are formed on the basis of common characteristics as, among others, personality. Thus, the aim of this study was to examine the mediation role of peers in the association between the five-factor model of personality and adolescent alcohol use in two cultures. One hundred and twenty Scottish and 221 Spanish respondents, all aged 12-15 years, answered the Alcohol Intake Scale (AIS). Adolescents were asked about the alcohol used at the weekend and also about the alcohol consumed by their friends. Scottish adolescents' personality was measured by the NEO Personality Inventory-3 (NEO-PI-3). The Junior Spanish version of the Revised NEO Personality Inventory (JS NEO) was used to assess personality in the Spanish sample. Low agreeableness and low conscientiousness correlated with own alcohol quantity in both countries. We performed an independent structural equation modeling for each country. Extraversion (β = .205, p < .05) and low agreeableness (β = -.196, p < .01) for Scottish adolescents, and low conscientiousness (β = -.175, p < .05) for Spanish youths, predicted alcohol use through peer alcohol consumption at weekends. These findings support the relevance of personality traits and peer affiliation in relation to alcohol consumption in adolescence.

Post-GWAS in Psychiatric Genetics: A Developmental Perspective on the "Other" Next Steps

As psychiatric genetics enters an era where gene identification is finally yielding robust, replicable genetic associations and polygenic risk scores, it is important to consider next steps and delineate how that knowledge will be applied to ultimately ameliorate suffering associated with substance use and psychiatric disorders. Much of the post-genome-wide association study discussion has focused on the potential of genetic information to elucidate the underlying biology and use this information for the development of more effective pharmaceutical treatments. In this review we focus on additional areas of research that should follow gene identification. By taking genetic findings into longitudinal, developmental studies, we can map the pathways by which genetic risk manifests across development, elucidating the early behavioral manifestations of risk, and studying how various environments and interventions moderate that risk across developmental stages. The delineation of risk across development will advance our understanding of mechanism, sex differences and risk and resilience processes in different racial/ethnic groups. Here, we review how the extant twin study literature can be used to guide these efforts. Together, these new lines of research will enable us to develop more informed, tailored prevention and intervention efforts.

Developmental Etiologies of Alcohol Use and Their Relations to Parent and Peer Influences Over Adolescence and Young Adulthood: A Genetically Informed Approach

BACKGROUND

Distinct changes in alcohol use etiologies occur during adolescence and young adulthood. Additionally, measured environments known to influence alcohol use such as peers and parenting practice can interact or be associated with this genetic influence. However, change in genetic and environmental influences over age, as well as how associations with measured environments change over age, is understudied.

METHODS

The National Longitudinal Study of Adolescent Health (Add Health) sibling subsample was used to examine data-driven biometric models of alcohol use over ages 13 to 27. Associations between friends' drinking, parental autonomy granting, and maternal closeness were also examined.

RESULTS

The best-fitting model included a 5-factor model consisting of early (ages 13 to 20) and overall (ages 13 to 27) additive genetic and unique environmental factors, as well as 1 overall common environment factor. The overall additive genetic factor and the early unique environment factor explained the preponderance of mean differences in the alcohol use over this portion of the life span. The most important factors explaining variance attributed to alcohol use changed over age. Additionally, friend use had the strongest associations with genetic and environmental factors at all ages, while parenting practices had almost no associations at any age.

CONCLUSIONS

These results supplement previous studies indicating changes in genetic and environmental influences in alcohol use over adolescence and adulthood. However, prior research suggesting that constraining exogenous predictors of genetic and environmental factors to have effects of the same magnitude across age overlooks the differential role of factors associated with alcohol use during adolescence. Consonant with previous research, friend use appears to have a more pervasive influence on alcohol use than parental influence during this age. Interventions and prevention programs geared toward reducing alcohol use in younger populations may benefit from focus on peer influence.

A National Swedish Longitudinal Twin-Sibling Study of alcohol use disorders among males

AIMS

To examine whether genetic influences on the development of alcohol use disorders (AUD) among men during emerging adulthood through mid-adulthood are stable or dynamic.

DESIGN

A twin study modeling developmental changes in the genetic and environmental influences on AUD during three age periods (18-25, 26-33 and 33-41) as a Cholesky decomposition.

SETTING

Sweden.

PARTICIPANTS

Swedish male twin pairs (1532 monozygotic and 1940 dizygotic) and 66 033 full male sibling pairs born less than 2 years apart.

MEASUREMENTS

AUD was identified based on Swedish medical and legal registries.

FINDINGS

The best-fitting model included additive genetic and unique environmental factors, with no evidence for shared environmental factors. Although the total heritability was stable over time, there were two major genetic factors contributing to AUD risk, one beginning at ages 18-25 with a modest decline in importance over time [0.84; confidence interval (CI) = 0.83-0.88], and another of less impact beginning at ages 26-33 with a modest increase in importance by ages 33-41 (0.31; CI = 0.05-0.47).

CONCLUSIONS

The heritability of alcohol use disorders among Swedish men appears to be stable among three age periods: 18-25 years, 26-33 years, and 33-41 years. Two sets of genetic risk factors contribute to alcohol use disorders risk, with one originating during the ages 18-25 years and another coming online at 26-33 years, providing support for the developmentally dynamic hypothesis.

Contributions of Genes and Environment to Developmental Change in Alcohol Use

The precise nature of how genetic and environmental risk factors influence changes in alcohol use (AU) over time has not yet been investigated. Therefore, the aim of the present study is to examine the nature of longitudinal changes in these risk factors to AU from mid-adolescence through young adulthood. Using a large sample of male twins, we compared five developmental models that each makes different predictions regarding the longitudinal changes in genetic and environmental risks for AU. The best-fitting model indicated that genetic influences were consistent with a gradual growth in the liability to AU, whereas unique environmental risk factors were consistent with an accumulation of risks across time. These results imply that two distinct processes influence adolescent AU between the ages of 15-25. Genetic effects influence baseline levels of AU and rates of change across time, while unique environmental effects are more cumulative.

The association between personality disorders with alcohol use and misuse: A population-based twin study

BACKGROUND

A clearer understanding of the etiological overlap between DSM-IV personality disorders (PDs) and alcohol use (AU) and alcohol use disorder (AUD) is needed. To our knowledge, no study has modeled the association between all 10 DSM-IV PDs and lifetime AU and AUD. The aim of the present study is to identify which PDs are most strongly associated with the phenotypic, genetic, and environmental risks of lifetime AU and AUD, and to determine if these associations are stable across time.

METHODS

Participants were Norwegian twins assessed at two waves. At Wave 1, 2801 twins were assessed for all 10 DSM-IV PD criteria, lifetime AU, and DSM-IV AUD criteria. At Wave 2, six of the 10 PDs were again assessed along with AU and AUD among 2393 twins. Univariate and multiple logistic regressions were run. Significant predictors were further analyzed using bivariate twin Cholesky decompositions.

RESULTS

Borderline and antisocial PD criteria were the strongest predictors of AU and AUD across the two waves. Despite moderate phenotypic and genetic correlations, genetic variation in these PD criteria explained only 4% and 3% of the risks in AU, and 5% to 10% of the risks in AUD criteria, respectively. At Wave 2, these estimates increased to 8% and 23% for AU, and 17% and 33% for AUD.

CONCLUSIONS

Among a large Norwegian twin sample, borderline and antisocial PD criteria were the strongest predictors of the phenotypic and genotypic liability to AU and AUD. This effect remained consistent across time.

Sweetened ethanol drinking during social isolation: enhanced intake, resistance to genetic heterogeneity and the emergence of a distinctive drinking pattern in adolescent mice

With its ease of availability during adolescence, sweetened ethanol ('alcopops') is consumed within many contexts. We asked here whether genetically based differences in social motivation are associated with how the adolescent social environment impacts voluntary ethanol intake. Mice with previously described differences in sociability (BALB/cJ, C57BL/6J, FVB/NJ and MSM/MsJ strains) were weaned into isolation or same-sex pairs (postnatal day, PD, 21), and then given continuous access to two fluids on PDs 34-45: one containing water and the other containing an ascending series of saccharin-sweetened ethanol (3-6-10%). Prior to the introduction of ethanol (PDs 30-33), increased water and food intake was detected in some of the isolation-reared groups, and controls indicated that isolated mice also consumed more 'saccharin-only' solution. Voluntary drinking of 'ethanol-only' was also higher in a subset of the isolated groups on PDs 46-49. However, sweetened ethanol intake was increased in all isolated strain × sex combinations irrespective of genotype. Surprisingly, blood ethanol concentration (BEC) was not different between these isolate and socially housed groups 4 h into the dark phase. Using lickometer-based measures of intake in FVB mice, we identified that a predominance of increased drinking during isolation transpired outside of the typical circadian consumption peak, occurring ≈8.5 h into the dark phase, with an associated difference in BEC. These findings collectively indicate that isolate housing leads to increased consumption of rewarding substances in adolescent mice independent of their genotype, and that for ethanol this may be because of when individuals drink during the circadian cycle.

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.