Introduction : There is concern that recreational marijuana legalization (RML) may lead to increased cannabis use disorder (CUD) among youth due to increased marijuana use. This study investigates whether adolescent substance use disorder treatment admissions for marijuana use increased in Colorado and Washington following RML.

Methods : Annual data on 2008-2017 treatment admissions for marijuana use from the SAMHSA TEDS-A dataset for adolescents age 12-17 were used to model state treatment admissions trends. Difference-in-differences models were used to investigate whether treatment admissions increased following RML in Colorado/Washington compared to non-RML states, after adjusting for socioeconomic characteristics and treatment availability.

Results : Over all states in the analysis, the rate of adolescent treatment admissions for marijuana use declined significantly over the study period (β=-3.375, 95 % CI=-4.842, -1.907), with the mean rate falling nearly in half. The decline in admissions rate was greater in Colorado and Washington compared to non-RML states following RML, though this difference was not significant (β=-7.671, 95 % CI=-38.798, 23.456).

Conclusion : Adolescent treatment admissions for marijuana use did not increase in Colorado and Washington following RML. This may be because youth marijuana use did not increase, CUD did not increase (even if use did increase), or treatment seeking behaviors changed due to shifts in attitudes and perceptions of risk towards marijuana use.