Statewide medical marijuana laws (MMLs) in the U.S. may be associated with adolescent marijuana use behavior, attitudes toward marijuana use, and social norms. This study used data from the National Study on Drug Use and Health (2013-2016) to examine the associations of state MML with marijuana use, use frequency, and attitudes and perceived peer and parental social norms toward using marijuana. Propensity-score matching was used to reduce selection bias between states with and without MML (matched N = 50,000). Results showed that adolescents residing in states with MML had higher odds of using marijuana in the past month and past year (OR = 1.45 and 1.49; s < .001), higher marijuana use frequencies in the past month (= 0.12, < .001), relatively more neutral attitudes toward marijuana use (= - 0.06, < .001), and weaker perception of peer and parental disapproval of marijuana use (= - 0.04 and -0.02, s < .001). Our findings suggested that for the states that have implemented MML, special efforts should be strengthened to prevent and reduce adolescent marijuana use. For the states that have not yet implemented MML, the associations between MML and adolescent marijuana use attitudes and perceived norms should be taken into account when legislating medical marijuana and designing prevention and intervention efforts.
