Long-term effects of minimum legal drinking age laws on marijuana and other illicit drug use in adulthood

Background: Exposure to permissive minimum legal drinking age (MLDA) laws (ability to purchase alcohol <21 years) during adolescence can have long-term effects, including heavy alcohol use or alcohol use disorders as adults. We examined whether exposure to permissive MLDA laws during adolescence has long-term effects on illicit drug use and disorders in adulthood. Methods: Participants from the 2004-2012 National Survey of Drug Use and Health (NSDUH) were linked with historical state MLDA laws. Participants born in 1949-1972 (age 31-63 years at observation, n= 110,300) were analyzed because they came of legal age for alcohol purchase when changes occurred in state MLDA laws. Logistic regression was used to model drug use measures as a function of exposure to permissive MLDA during adolescence, adjusting for state and birth-year fixed effects, demographics, and salient state characteristics. Results: Rates of past month use, past year use, and abuse/dependence of marijuana were 4.7%, 7.8%, and 1.2%, respectively. Rates of past month use, past year use, and abuse/dependence of illicit drugs other than marijuana were 2.9%, 6.2%, and 0.7%, respectively. Among the full sample, exposure to permissive MLDA laws was not significantly associated with drug use or abuse/dependence in adulthood. Men exposed to permissive MLDA laws were at 20% increased odds of past year illicit drug use (aOR 1.20, 95% CI 1.09-1.32). Conclusions: Restricting alcohol access during adolescence did not increase long-term drug use. Allowing the purchase of alcohol among those less than 21 years of age could increase the risk of drug use later in life.