Recreational Cannabis Markets Increased Use Across All Age Groups, Especially Older Adults

Using the synthetic control method, recreational cannabis markets were associated with moderate increases in adolescent use prevalence and initiation (11% and 13%), large increases among young adults 18-25 (17% and 33%), and the largest increases among adults 26+ (33% prevalence increase, 82% initiation increase) within 2-4 years of dispensary opening.

Synthetic control method with staggered treatment adoption applied to state-level data from the National Survey on Drug Use and Health. Five states analyzed: Colorado, Washington, Oregon, Alaska, and Nevada. Synthetic controls were constructed from non-legalizing states matched on pre-treatment demographics and cannabis use trends. Jackknife confidence intervals were used.

This study uses one of the strongest causal inference methods available for policy evaluation. The finding that older adults showed the largest increases challenges the focus on youth in cannabis policy debates and suggests that recreational markets are primarily expanding use among populations that were not previously using.

The 82% increase in initiation among adults 26+ is striking and suggests that legal retail access is creating a large new population of cannabis users who would not have otherwise tried the drug. Whether this translates to increased health harms or relatively benign experimentation remains to be determined.

Only five early-legalizing states were included; later states may show different patterns. The NSDUH data relies on self-report and may undercount use. The 2-4 year follow-up window may not capture longer-term trends. Synthetic controls cannot account for all possible confounders.