Non-medical marijuana laws (MMLs) enacted in US states are associated with increased marijuana use, but only among adults aged ≥26 years, according to a recent study. Participants comprised 2004–2013 National Survey of Drug Use and Health (NSDUH) respondents (n~67,500/year); age groups 12–17, 18–25, and ≥26 years. Primary outcome measures included (1) active (past-month) marijuana use; (2) heavy use (> 300 days/year); and (3) cannabis use disorder diagnosis, based on DSM-IV criteria. Researchers found:

• Adults aged ≥26 years living in states with non-medical MML programs increased past-month marijuana use 1.46% (from 4.13 to 6.59%), skewing towards greater heavy marijuana use by 2.36% (from 14.94 to 17.30%) after MMLs were enacted.
• However, no associated increase in the prevalence of cannabis use disorder was found during the study period.
• There were no increases in prevalence of marijuana use among adults in states with medicalized MML programs.
• Additionally, there were no increases in adolescent or young adult marijuana outcomes following MML passage, irrespective of program type.