A Longitudinal Adoption Study of Substance Use Behavior in Adolescence.

Although cross-sectional twin studies have assessed the genetic and environmental etiologies of substance use during adolescence and early adulthood, comparisons of results across different samples, measures, and cohorts are problematic. While several longitudinal twin studies have investigated these issues, few corroborating adoption studies have been conducted. The current study is the first to estimate the magnitude of genetic, shared environmental, and non-shared environmental influences on substance use (cigarettes, alcohol, and marijuana) from ages 14 to 18 years, using a prospective longitudinal adoption design.

Gender moderates the association between 5-HTTLPR and decision-making under ambiguity but not under risk.

Decisions made under ambiguity may involve a different genetic architecture than those made under risk. Because gender moderates the effect of genetic polymorphisms on serotonin function and because there are gender differences in decision-making, the present study examined potential gender moderation of associations between polymorphisms in important serotonin system candidate genes (serotonin transporter [SLC6A4] and tryptophan hydroxylase-2 [TPH2]) and performance on a decision-making task (Iowa Gambling Task, IGT) in healthy, adults (N = 188; 62% women). Subjects were genotyped for the well-studied SLC6A4 promoter variant 5-HTTLPR and a TPH2 single nucleotide polymorphism in intron-8 (rs1386438).