Impact of cannabis legalization on healthcare utilization for psychosis and schizophrenia in Colorado
G. S. Wang, Christine Buttorff, Asa Wilks, D. Schwam, G. Tung, R. Pacula
International Journal of Drug Policy April 13, 2022 DOI: 10.1016/j.drugpo.2022.103685 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study using difference-in-difference analysis of administrative data Peer reviewed |
|---|---|
| Population | County-level quarterly emergency department visits in Colorado from January 1, 2013, to December 31, 2018 |
| Topics | Cannabis |
| Key findings | As recreational cannabis dispensaries per 10,000 residents increased, psychosis-related emergency department visits rose 24% (IRR 1.24, 95% CI 1.02-1.49), while schizophrenia visits showed no significant association (IRR 0.95, 95% CI 0.69-1.30). Counties with low baseline medical dispensary exposure had smaller increases in psychosis visits than those with high baseline exposure (IRR 0.83, 95% CI 0.69-0.99). The authors suggest a potential impact on local mental health after cannabis legalization. |
Abstract
Background: Emergency department (ED) visits involving psychosis and schizophrenia have increased at a rate exceeding population growth in the United States over the past decade. Research shows a strong dose-response relationship between chronic use of high-potency cannabis and odds of developing symptoms of psychosis. The aim of this study was to evaluate the impact of cannabis legalization on psychosis and schizophrenia-related ED visits in Colorado.
Methods: Using administrative data from Colorado Hospital Association (CHA) on county-level quarterly ED visits between January 1, 2013, and December 31, 2018, we applied a difference-in-difference analysis to examine how new exposure to recreational cannabis dispensaries after 2014 differentially influenced the rate of ED visits for psychosis and schizophrenia, comparing counties with no prior medical cannabis dispensary exposure to counties with low or high medical dispensary exposure.
Results: As recreational dispensaries per 10,000 residents increased, there was no significant association with the rate of schizophrenia ED visits per capita (incidence rate ratio or IRR: 0.95, 95% CI [0.69, 1.30]) while the rate of psychosis visits increased 24% (IRR: 1.24, 95% CI [1.02, 1.49]). Counties with no previous medical dispensaries experienced larger increases in schizophrenia ED visits than counties already exposed to a low level of medical dispensaries, but this effect was not significant. Counties with low baseline medical exposure had lower increases in rates of psychosis visits than counties with high baseline medical exposure (IRR 0.83, 95% CI [0.69, 0.99]).
Conclusions: There was a positive association between the number of cannabis dispensaries and rates of psychosis ED visits across all counties in Colorado. Although it is unclear whether it is access to products, or the types of products that may be driving this association, our findings suggest there is a potential impact on the mental health of the local population that is observed after cannabis legalization.
Comparable studies
Other observational and cohort studies on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population | 2009 | Case-control study | n = 454 |
| Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population | 2013 | Observational study | |
| Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people | 2000 | Observational | |
| Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline | 2011 | Observational cohort | n = 1,923 |
| Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... | 2005 | Observational cohort | n = 535 |
Citations in the library
Cited by 5
- Cannabis use and psychosis among patients hospitalized in psychiatric wards in Lebanon: a retrospective chart review Middle East Current Psychiatry November 13, 2023
- The subjective effects of △9-tetrahydrocannabinol: A systematic review and dose-response meta-regression. Neuroscience & Biobehavioral Reviews June 3, 2026
- [Impact of the legalization of recreational cannabis on the risk of psychosis: A systematic review of the literature]. L'Encephale September 1, 2024
- Cannabis use among patients presenting to the emergency department for psychosis: Associations with restraint use, medication administration, psychiatric hospitalization, and repeat visits. Psychiatry Research March 17, 2023
- Cannabis Use Patterns in First Episode Psychosis and Schizophrenia: A Scoping Review and Case Series
Cites 7
- Will Legalization and Commercialization of Cannabis Use Increase the Incidence and Prevalence of Psychosis? JAMA Psychiatry April 8, 2020
- Annual incidence of cannabis-induced psychosis, other substance-induced psychoses and dually diagnosed schizophrenia and cannabis use disorder in Denmark from 1994 to 2016 Psychological Medicine December 16, 2019
- The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study The Lancet Psychiatry May 1, 2019
- The association between cannabis abuse and subsequent schizophrenia: a Swedish national co-relative control study. Psychological Medicine January 2015
- Synthetic delta-9-tetrahydrocannabinol elicits schizophrenia-like negative symptoms which are distinct from sedation. Human psychopharmacology January 2011
and 2 more in the library