Associations Between Parental Marijuana Use from Adolescence to Adulthood and Subsequent Substance Use and Norms in Their Children

Introduction: The recent legalization of marijuana in several states has increased public health concern over the consequences of marijuana use. This is particularly relevant to adult legal users, some of whom are actively parenting children and adolescents. Parent marijuana use has been widely linked to adverse effects on child well-being, including a higher likelihood of child substance use. Most studies focus on parents’ current use, and a few have demonstrated that heavy prior use is problematic. However, little is known about whether different developmental patterns of marijuana use among parents impact children differently. For example, is the effect of parents’ light or infrequent marijuana use on child outcomes similar to the effect of nonuse or to chronic use?

 Methods: The study uses data from two longitudinal studies, the Seattle Social Development Project (SSDP) which followed participants (N = 808) from ages 10 to 39, and the SSDP Intergenerational Study (TIP), which has collected data on a subset of SSDP participants and their children (N = 383). Previous analyses using SSDP data found four discrete trajectories of marijuana use from age 14 to 30: nonuser (27% of SSDP participants), late onset light (20%), adolescent-limited (21%), and chronic users (32%). Current study examined how the parent marijuana use trajectories (controlling for current parent marijuana use) predicted child ever use of marijuana, alcohol, and cigarettes, and child pro-substance use norms.

 Results: Children of chronic and adolescent-limited users were most likely to have used marijuana in their lifetime. Children of parents who used heavily in adolescence (adolescent limited) were most likely to use cigarettes and held the most pro-substance use norms. Children of late onset light users did not differ from children of nonusers in their substance use. Parent marijuana use trajectory was largely unrelated to children’s use of alcohol.

 Implications for prevention: Within a legalized marijuana context, it is important to understand that marijuana use can have long-lasting implications, even into the next generation, even if the parent desists marijuana use. Marijuana use among children of the chronic and adolescent-limited parental use groups showed the greatest impact on their children’s substance use, whereas infrequent parental marijuana use later in life may be less harmful. Prevention program reducing adolescent marijuana use may thus have benefits that extend beyond the immediate target sample into the next generation.