More cannabis dispensaries in Colorado counties were linked to 24% more psychosis ER visits | Research

The takeaway

After recreational cannabis legalization in Colorado, increasing dispensary density was associated with a 24% increase in psychosis-related ER visits, while schizophrenia visits showed no significant change.

Policymakers considering cannabis legalization, mental health system planners, and researchers studying legalization impacts.

24% increase in psychosis ER visits with increasing dispensary density

What the researchers found

As recreational dispensaries per 10,000 residents increased, psychosis ED visits increased 24% (IRR 1.24, 95% CI 1.02-1.49) while schizophrenia ED visits showed no significant change (IRR 0.95). Counties previously unexposed to medical dispensaries may have experienced larger increases.

Why it matters

This is one of the first studies to use a natural experiment design to examine whether cannabis dispensary access directly impacts psychosis-related healthcare utilization at the population level.

The numbers in context

Psychosis ED visits: IRR 1.24 (significant). Schizophrenia ED visits: IRR 0.95 (not significant). Counties with low baseline medical exposure had lower psychosis increases than high-exposure counties (IRR 0.83).

How the study worked

Difference-in-difference analysis of Colorado Hospital Association county-level quarterly ED data from January 2013 to December 2018. Compared how new recreational dispensary exposure affected psychosis and schizophrenia ED visit rates across counties with different baseline medical dispensary exposure.

What this study cannot tell us

Observational, cannot prove causation. Administrative coding may not distinguish cannabis-induced psychosis from other causes. Dispensary density may correlate with other county-level factors. Short post-legalization period.

How to read the evidence

Moderate: natural experiment design with administrative data, but observational with potential confounders.

When this study was published

Published in 2022.

The bigger picture

The association between dispensary density and psychosis visits raises important questions for states and countries considering legalization, particularly regarding the mental health impact of increased cannabis availability.

Questions still open

Is it the number of dispensaries, the type of products available, or increased overall use driving psychosis visits? Why was schizophrenia not affected? Would the same pattern be seen in other legalized states?

Common questions

Does this prove dispensaries cause psychosis?

No. It shows an association between dispensary density and psychosis-related ER visits. The increase could be driven by greater cannabis access, higher-potency products, more use, or increased willingness to seek emergency care.

Why did schizophrenia visits not increase?

The authors suggest psychosis ED visits may capture acute cannabis-related episodes more than chronic schizophrenia. Schizophrenia diagnoses tend to be established conditions less responsive to changes in cannabis access.

Did prior medical dispensary exposure matter?

Yes. Counties that already had medical dispensaries before recreational legalization appeared somewhat buffered from the increase, possibly because they had already absorbed some cannabis-related mental health impact.

Read the original research

Impact of cannabis legalization on healthcare utilization for psychosis and schizophrenia in Colorado.

The International journal on drug policy, 104, 103685

View on PubMed ↗Publisher’s paper ↗

Citation

Wang, George Sam; Buttorff, Christine; Wilks, Asa; Schwam, Daniel; Tung, Gregory; Pacula, Rosalie Liccardo. (2022). Impact of cannabis legalization on healthcare utilization for psychosis and schizophrenia in Colorado.. The International journal on drug policy, 104, 103685. https://doi.org/10.1016/j.drugpo.2022.103685