Understanding the links between parental and adolescent substance use:complementary natural experiments using the children of twins design

PROJECT SUMMARY A fundamental question in human development is how and to what extent parents shape the behavior of their children. Current perspectives on the intergenerational transmission of substance use and disorder have been greatly influenced by longstanding socialization theories of parental modeling and problematic parenting. At the same time, substance use and disorder are heritable and substance using parents also pass genetic liability to use substances to their children. Identifying causal mechanisms of intergenerational transmission is critical to develop and implement effective preventive–intervention efforts, but observational studies of nuclear families and parent–child dyads fully confound socialization and genetic influences. Effects of parental substance use within families are particularly salient now, in the context of rapid shifts in marijuana legality, availability, and acceptability. We will examine the intergenerational impact of parental marijuana use using two complementary natural experiments — the children of twins design and a comparison of two states with markedly different marijuana laws — in 6,457 parents and adolescents from 1,902 families in Colorado and Minnesota. Twin parents are participants in the Colorado–Minnesota Marijuana Study (DA042755), a collaboration between two genetically informative, longitudinal twin studies with parallel, multi-wave, longitudinal measures that are conducted in two states with marked differences in current marijuana legality and availability. We now intend to recruit and twins’ adolescent children, and nontwin parents/caregivers, to evaluate parent–child transmission of marijuana use and disorder. The following specific aims will be addressed: (1) Differentiate mechanisms of parent–child transmission of marijuana use and disorder using an innovative children of twins design; (2) Determine effects of marijuana legalization on parents, families, and adolescents by comparing parental and adolescent marijuana use, parenting practices, and the family environment in two states with markedly different marijuana laws; and (3) Delineate effects of behavioral disinhibition in the context of marijuana legalization, testing the hypothesis that parents and adolescents with greater disinhibition will use marijuana at higher rates and/or with more problems in Colorado. Leveraging these uniquely informative, complementary study designs, as well as the comprehensive longitudinal data already collected in these twin samples, we will be able to answer important questions about the intergenerational transmission of substance use in a rapidly changing landscape —legalized recreational marijuana — with critical implications for prevention and intervention efforts and public policy.