Testosterone and alcohol use among adolescent male twins: testing between-family associations in within-family comparisons.

We examined associations of testosterone (T) and alcohol use in adolescent twin brothers, conducting both between- and within-family analyses. The twins completed semi-structured interviews, provided two saliva samples to assay T, and reported their drinking patterns and pubertal development. We adjusted T levels for diurnal/seasonal effects and association with pubertal maturation. In analyses of twins as individuals, higher T levels characterized boys reporting ever drinking, more frequent intoxication, high density drinking, more alcohol symptoms, and diagnosed alcohol dependency on interview. Adjusting for pubertal development, only associations with symptom count and diagnosis remained significant. The association with frequent intoxication replicated among drinking-discordant twin brothers, effectively ruling out between-family confounds, but that association was not significant after adjustment for pubertal development. The phenotypic correlation between T and pubertal maturation is largely genetic, inviting study of the magnitude and meaning of linkages between testosterone and symptoms of alcoholism on follow-up in early adulthood.