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Background and Aims: Previous studies have demonstrated associations between substance use and reduced educational attainment; however, many were unable to account for potential confounding factors like genetics and the rearing environment. In the few studies that controlled for these factors, the substances assessed were limited to alcohol, cannabis, and tobacco. To address these limitations, we examined the relationship between adolescent use of seven kinds of substances, the number of additional substances used, and high school noncompletion within a large sample of Australian twins. Design: A series of two‐level generalized mixed effects logistic regressions were conducted to examine associations between adolescent substance use and high school noncompletion. Setting: Australia. Participants: A total of 9579 adult Australian twins from two cohorts of the Australian Twin Registry. Measurements Assessments of high school completion, childhood major depression, conduct disorder symptoms, substance use initiation, demographics, and parental educational attainment using the Australian version of the Semi‐Structured Assessment for the Genetics of Alcoholism. Findings There were unique within‐twin‐pair effects of use of sedatives (odds ratio [OR] = 22.39 [95% confidence interval (CI) = 1.18–423.48]) and inhalants/solvents (OR = 10.46 [95% CI = 1.30–84.16]) on high school noncompletion. The number of substances used in adolescence was strongly associated with high school noncompletion across all discordant twin models (ORs from 1.50–2.32, Ps < 0.03). Conclusions: In Australia, adolescent substance use appears to be associated with early school dropout, with the effects of any given substance largely because of the confounding factors of parental education, childhood conduct disorder symptoms, and use of other substances. Sedatives and inhalants/solvents have effects on high school noncompletion that cannot be explained by polysubstance use or familial factors. [ABSTRACT FROM AUTHOR]

Background and Aims: Previous research has demonstrated phenotypical associations between disordered gambling (DG) and Big 5 personality traits, and a twin study suggested that shared genetic influences accounted for a substantial portion of this relation. The present study examined associations between DG and polygenic scores (PSs) for Big 5 traits to measure the shared genetic underpinnings of Big 5 personality traits and DG. Design: Zero-inflated negative binomial regression models estimated associations between Big 5 PSs and past-year and life-time assessments of DG in a longitudinally assessed population-based birth cohort. Setting: United Kingdom. Participants: A total of 4729 unrelated children of European ancestry from the Avon Longitudinal Study of Parents and Children (ALSPAC) with both phenotypical and genetic data. Measurements: Phenotypical outcomes included past-year assessment of DG using the problem gambling severity index (PGSI) and life-time assessment of DSM-IV pathological gambling symptoms (DPG) across the ages of 17, 20 and 24 years. Polygenic scores were derived for the Big 5 personality traits of agreeableness, extraversion, conscientiousness, openness and neuroticism using summary statistics from genome-wide association studies (GWAS). Findings: PSs for agreeableness [ß= - 0.25, standard error (SE) = 0.054, P = 3.031e-6, ΔR2 = 0.008] and neuroticism (ß=0.14, SE = 0.046, P = 0.0017, ΔR2 = 0.002) significantly predicted PGSI scores over and above included covariates (i.e. sex and first five ancestral principal components). PSs for agreeableness (ß= - 0.20, SE = 0.056, P = 0.00036, ΔR2 = 0.003) and neuroticism, when interactions with age were taken into account (ß = 0.29, SE = 0.090, P = 0.002, ΔR2 = 0.004), also predicted DPG scores. Conclusions: Polygenic contributions to low agreeableness and high neuroticism appear to predict two measures of disordered gambling (problem gambling severity index and life-time assessment of DSM-IV pathological gambling symptoms). Polygenic scores for neuroticism interact with age to suggest that the positive association becomes stronger from adolescence through young adulthood. [ABSTRACT FROM AUTHOR]

Aims: To identify drug use typologies based on substances used and persistence of use over two time points, use a genetically informed design to explore twin concordance of and genetic influence on the use typologies and compare patterns of declined/discontinued ("desistant") and persistent drug use on drug use correlates. Design Latent class analysis was applied to data from a cross‐sectional self‐report survey on current and past drug use. Use characteristics, use disorder, and psychiatric problems were compared across classes. Setting: Computer‐assisted telephone interview in respondents' homes. Participants: A total of 3785 individual twins and siblings (1365 men, 2420 women; Mage = 32) from the Australian Twin Registry Cohort III. Measurements A comprehensive interview assessed prior to past year and past year use of cannabis, stimulants, cocaine/crack, hallucinogens, opioids, sedatives, inhalants, dissociatives, and solvents; age of first use; opportunity to use; peer drug use; attention deficit/hyperactivity, conduct, antisocial personality, depressive, and substance use disorders; and suicidality. Findings A five‐class solution emerged: no/low use (50%), desistant cannabis use (23%), desistant party drug use (18%), persistent prescription drug misuse (4%), and persistent polydrug use (5%). Twin concordances were higher among monozygotic (k = 0.30–0.35) than dizygotic pairs (same‐sex k = 0.19–0.20; opposite sex k = 0.07), and biometric modeling suggested that the persistent polydrug use class, in particular, was highly heritable (a2 = 0.94). Conduct disorder (OR = 2.40), antisocial personality disorder (OR = 3.27), and suicidal ideation (OR = 1.98) increased persistent polydrug use risk; depression (OR = 2.38) and lifetime suicide attempt (OR = 2.31) increased persistent prescription misuse risk. Relative to persistent prescription drug misuse, persistent polydrug use was associated with higher rates of cannabis and stimulant use disorder (OR = 6.14–28.01), younger first substance use (OR = 0.82–0.83), more drug use opportunity (OR = 10.66–66.06), and more drug‐using peers (OR = 4.66–9.20). Conclusions: Unique patterns of declined/discontinued ("desistant") and persistent drug use are differentially heritable and differentially associated with risk factors, psychiatric symptoms, and substance use disorder outcomes. [ABSTRACT FROM AUTHOR]