The Effect of Medical Marijuana Laws on Marijuana-Related Attitude and Perception Among US Adolescents and Young Adults.

Marijuana liberalization policies are gaining momentum in the USA, coupled with limited federal interference and growing dispensary industry. This evolving regulatory landscape underscores the importance of understanding the attitudinal/perceptual pathways from marijuana policy to marijuana use behavior, especially for adolescents and young adults. Our study uses the restricted-access National Survey on Drug Use and Health (NSDUH) 2004-2012 data and a difference-in-differences design to compare the pre-policy, post-policy changes in marijuana-related attitude/perception between adolescents and young adults from ten states that implemented medical marijuana laws during the study period and those from the remaining states. We examined four attitudinal/perception pathways that may play a role in adolescent and young adult marijuana use behavior, including (1) perceived availability of marijuana, (2) perceived acceptance of marijuana use, (3) perceived wrongfulness of recreational marijuana use, and (4) perceived harmfulness of marijuana use. We found that state implementation of medical marijuana laws between 2004 and 2012 was associated with a 4.72% point increase (95% CI 0.15, 9.28) in the probability that young adults perceived no/low health risk related to marijuana use. Medical marijuana law implementation is also associated with a 0.37% point decrease (95% CI - 0.72, - 0.03) in the probability that adolescents perceived parental acceptance of marijuana use. As more states permit medical marijuana use, marijuana-related attitude/perception need to be closely monitored, especially perceived harmfulness. The physical and psychological effects of marijuana use should be carefully investigated and clearly conveyed to the public.