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AbstractA prospective study of 692 male twins was undertaken to investigate the relationships among early adolescent problem behavior, contextual risk, and disinhibitory psychopathology. Early adolescent problem behavior was assessed by the number of the following behaviors engaged in by the time of the age-14 assessment: (1) tobacco use, (2) alcohol use, (3) marijuana use, (4) other illicit drug use, (5) sexual intercourse, and (6) police contact. Contextual risk was assessed as a composite of measures of peer models, parent-offspring conflict, and academic engagement from the age-14 assessment. Disinhibitory psychopathology was assessed by symptoms of nicotine dependence, alcohol dependence, drug dependence, and adult antisocial behavior at the age-18 assessment. Early adolescent problem behavior and contextual risk were strongly correlated (r = .53) and both were strongly and independently associated with symptoms of disinhibitory psychopathology (r from .35 to .60). The association of early adolescent problem behavior with both contextual risk and disinhibitory psychopathology was mediated entirely by genetic factors while the association between contextual risk and disinhibitory psychopathology was mediated by both genetic and nonshared environmental factors. The results are discussed in the context of emerging research on the prognostic significance of early adolescent problem behavior for risk of adult psychopathology.

Previous research has shown adolescent siblings are similar in their alcohol use and that this similarity is largely due to their shared environment. Using a genetically informed sibling sample (196 full‐biological pairs, 384 genetically unrelated pairs), we confirmed that the extent to which older siblings facilitate younger siblings' alcohol use (i.e., help them get alcohol) was one factor contributing to this shared environmental association. All analyses controlled for parent and peer influences. Findings were not moderated by sibling differences in genetic relatedness, gender, or ethnicity. Proximity in sibling age strengthened these associations, somewhat. Results were especially strong for sibling pairs where the older sibling was of legal drinking age. Implications for prevention and intervention are discussed.

AbstractThe Enrichment Study (ES) was designed to extend the Minnesota Twin Family Study (MTFS) by oversampling 11-year-old twins at especially high risk for substance use disorders by virtue of having a childhood disruptive disorder. The sample was ascertained from Minnesota birth records. To identify high-risk twins, we conducted telephone screening interviews for parent-reported symptoms of attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD) as well as indications of academic disengagement. Twins who exceeded a predetermined threshold were invited to participate. To facilitate comparison with the previously ascertained MTFS participants, a random sample of 11-year-old twins was also recruited. As part of the ES study, 499 twin pairs, and their parents, visited the University of Minnesota, where each participant completed a clinical interview, psychophysiological evaluation, and thorough assessment of environmental risk. We were highly successful in recruiting at-risk twins; 52% of the screened male twins and 41% of the screened females met criteria for a diagnosis of ADHD, CD, or oppositional defiant disorder (ODD). At the pair level, 63% of the screened pairs had at least one member with a childhood disruptive disorder. This article provides an overview of the study design and includes a review of recent findings using this sample of twins.