Young adult cannabis use increased more in states with full legalization than medical-only states | Research

The takeaway

Cannabis and blunt use among young adults increased in all 16 studied states between 2002-2018, but increases were larger in states with adult-use laws compared to medical-only states, particularly after retail outlets opened.

State policymakers considering cannabis legalization, public health officials, and researchers studying policy effects on substance use.

What the researchers found

All states showed declining cigarette smoking, slight cigar declines, and increasing cannabis and blunt use among young adults. Cannabis use increased following opening of medical retail outlets and further after adult-use implementation. In Maine, cannabis use increased 22.4% after medical retail opened and continued rising after adult use was adopted.

Why it matters

This provides evidence that cannabis legalization, particularly the opening of retail outlets rather than just passing laws, is associated with increased young adult use. The simultaneous decline in cigarette smoking suggests shifting substance preferences rather than simply adding a new substance.

The numbers in context

16 states studied (2002-2018). Maine: 22.4% increase in cannabis use (95% CI: 19.0-29.4) after medical retail opened. All states showed declining cigarette use. Cannabis and blunt use increased more in AMU vs MUO states.

How the study worked

Segmented regression analysis of National Survey on Drug Use and Health data (2002-2018) in 16 states that passed adult and medical use or medical-only cannabis laws. Past 30-day cannabis, blunt, cigarette, and cigar use examined.

What this study cannot tell us

Ecological study cannot prove individual-level causation. State-level trends are confounded by many other policy, economic, and cultural changes occurring simultaneously. NSDUH data may undercount some populations.

How to read the evidence

National survey data with appropriate segmented regression, but ecological design and multiple confounding state-level factors limit causal claims.

When this study was published

2025 publication analyzing 2002-2018 data.

The bigger picture

The finding that retail outlet opening, not law passage, appears to drive use increases has important implications for states considering legalization. Implementation details (when and how products become available) may matter more than the legal change itself.

Questions still open

Does the increase in cannabis use among young adults translate to increased harm?
Could delayed retail outlet opening after legalization reduce the initial surge in use?

Common questions

Does legalization cause more young adults to use cannabis?

This study shows an association between legalization (especially retail sales) and increased use, but cannot prove causation. Many other factors changed simultaneously in these states. The increases were modest and cigarette use declined.

Why does retail opening matter more than the law itself?

Laws create legal permission, but retail outlets create physical access. When cannabis becomes as easy to purchase as alcohol, use appears to increase. States that passed laws but delayed retail implementation saw use increases primarily after stores opened.

Read the original research

Temporal Trends in Young Adult Cannabis and Tobacco Use in States with Different Cannabis Policies.

Cannabis (Albuquerque, N.M.), 8(2), 98-111

View on PubMed ↗Publisher’s paper ↗

Citation

Glasser, Allison M; Uriarte, Caitlin; King Jensen, Jessica; Sterling, Kymberle; Shang, Ce; Hammond, David; Villanti, Andrea C. (2025). Temporal Trends in Young Adult Cannabis and Tobacco Use in States with Different Cannabis Policies.. Cannabis (Albuquerque, N.M.), 8(2), 98-111. https://doi.org/10.26828/cannabis/2025/000288