Aim To examine variation in positive and negative subjective effects to alcohol, tobacco and marijuana and covariation between these three drugs and each effect.
Design Retrospective self-reports of subjective effects were collected to estimate the genetic and environmental influences and the extent of their specificity across three drugs.
Participants Data were drawn from 1299 adolescent and young adult same- and opposite sex twin- and sibling-pairs participating in the Colorado Center for Antisocial Drug Dependence (CADD).
Setting A large, collaborative, longitudinal study of substance use and antisocial behavior in community and clinical adolescents.
Measurement Subjective effects were assessed using a 13-item questionnaire that included positive and negative responses to alcohol, tobacco and marijuana.
Findings Heritable influences contributed moderately (additive genetic effects 16–56%) to positive and negative subjective effects to all three drugs and did not differ for males and females. Genetic and environmental contributions to positive and negative subjective effects are largely non-overlapping for tobacco and marijuana. Multivariate genetic modeling indicated that subjective effects to alcohol, tobacco and marijuana share a common, heritable etiology and that drug-specific genetic influences were an important contributor to individual differences in drug response.
Conclusions Results from our genetic analyses suggest that subjective effects to these commonly used and misused drugs are heritable and that the genetic and environmental influences on effects to one drug also influence subjective effects to other drugs.