The Effect of Medical Marijuana Laws on Marijuana, Alcohol, and Hard Drug Use

21 states and the District of Columbia currently have laws that permit marijuana use for medical purposes, often termed medical marijuana laws (MMLs). We tested the effects of MMLs adopted in seven states between 2004 and 2011 on adolescent and adult marijuana, alcohol, and hard drug use. We employed a restricted-access version of the National Survey on Drug Use and Health (NSDUH) micro-level data with geographic identifiers. For those 21 and older, we found that MMLs led to a relative increase in the probability of marijuana use of 16 percent, an increase in marijuana use frequency of 12-17 percent, and an increase in the probability of marijuana abuse/dependence of 15-27 percent. For those 12-20 years old, we found a relative increase in marijuana use initiation of 5-6 percent. Among those aged 21 or above, MMLs increased the frequency of binge drinking by 6-9 percent, but MMLs did not affect drinking behavior among those 12-20 years old. MMLs had no discernible impact on hard drug use in either age group. Taken together, MML implementation increases marijuana use mainly among those over 21, where there is also a spillover effect of increased binge drinking, but there is no evidence of spillovers to other substance use.