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Cited by 41Cannabis and Cannabinoid ResearchSchizophrenia research and treatmentSubstance Abuse Treatment and Outcomes

Associations Between Canada's Cannabis Legalization and Emergency Department Presentations for Transient Cannabis-Induced Psychosis and Schizophrenia Conditions: Ontario and Alberta, 2015–2019

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Callaghan, Russell C., Sanches, Marcos, Murray, Robin M., Konefal, Sarah, Maloney-Hall, Bridget, Kish, Stephen J.·2022·The Canadian Journal of Psychiatry
DOI 10.1177/07067437211070650PMC PMC9301152
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Abstract

Objective: Cannabis legalization in many jurisdictions worldwide has raised concerns that such legislation might increase the burden of transient and persistent psychotic illnesses in society. Our study aimed to address this issue. Methods: Drawing upon emergency department (ED) presentations aggregated across Alberta and Ontario, Canada records (April 1, 2015–December 31, 2019), we employed Seasonal Autoregressive Integrated Moving Average (SARIMA) models to assess associations between Canada's cannabis legalization (via the Cannabis Act implemented on October 17, 2018) and weekly ED presentation counts of the following ICD-10-CA-defined target series of cannabis-induced psychosis (F12.5; n = 5832) and schizophrenia and related conditions (“schizophrenia”; F20-F29; n = 211,661), as well as two comparison series of amphetamine-induced psychosis (F15.5; n = 10,829) and alcohol-induced psychosis (F10.5; n = 1,884). Results: ED presentations for cannabis-induced psychosis doubled between April 2015 and December 2019. However, across all four SARIMA models, there was no evidence of significant step-function effects associated with cannabis legalization on post-legalization weekly ED counts of: (1) cannabis-induced psychosis [0.34 (95% CI −4.1; 4.8; P = 0.88)]; (2) schizophrenia [24.34 (95% CI −18.3; 67.0; P = 0.26)]; (3) alcohol-induced psychosis [0.61 (95% CI −0.6; 1.8; P = 0.31); or (4) amphetamine-induced psychosis [1.93 (95% CI −2.8; 6.7; P = 0.43)]. Conclusion: Implementation of Canada's cannabis legalization framework was not associated with evidence of significant changes in cannabis-induced psychosis or schizophrenia ED presentations. Given the potentially idiosyncratic rollout of Canada's cannabis legalization, further research will be required to establish whether study results generalize to other settings.

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  • The comparison of hospitalization rates before and after legalization in Callaghan et al. did not take account of the fact that cannabis-related psychiatric presentations were increasing before legalization of adult use.

    “The comparison of hospitalization rates before and after legalization did not take account of the fact that cannabis‐related psychiatric presentations were increasing before legalization of adult use.”

    From The implementation and public health impacts of cannabis legalization in Canada: a systematic review (2023) · cites this paper as [39]

    The Methods (Analytic Plan; page not available in our copy) say the authors fitted models to 185 weeks of pre-legalization data and used those models to forecast post-legalization presentations. The claim that their comparison did not account for the pre-legalization pattern is therefore contrary to the described analysis. The paper studies emergency-department presentations, not hospitalization rates. (LLM, conf=0.90)

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  • ED presentations for cannabis-induced psychosis doubled between April 2015 and December 2019 in Alberta and Ontario, but there was no significant increase associated with cannabis legalization.

    “ED presentations for cannabis‐induced psychosis doubled between April 2015 and December 2019, but there was no significant increase associated with cannabis legalization.”

    From The implementation and public health impacts of cannabis legalization in Canada: a systematic review (2023) · cites this paper as [39]

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Authors
Callaghan, R. C., Sanches, M., Murray, R. M., Konefal, S., Maloney-Hall, B., & Kish, S. J.
Affiliations
  • University of British Columbia (CA)
  • Centre for Addiction and Mental Health (CA)
  • King's College London (GB)
  • Canadian Centre on Substance Use and Addiction (CA)
  • Canadian Centre on Substance Use and Addiction, Ottawa, Ontario, Canada
Corresponding author
Callaghan, Russell C.
ORCID
Venue
The Canadian Journal of Psychiatry
Publisher
SAGE Publications
Published
2022-01-12
Volume
67
Issue
8
Pages
616-625
ISSN
  • 0706-7437 (ISSN-L)
  • 1497-0015
DOI
10.1177/07067437211070650
PMC
PMC9301152
OpenAlex
W4206014033
Cited by
41
References
5
Citations by year
2026: 6 · 2025: 9 · 2024: 11 · 2023: 12 · 2022: 3
FWCI
5.24
Type
journal article
Language
en
Open access
Licence
Locations
  • The Canadian Journal of Psychiatry (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Research Portal (King's College London) (publishedVersion, other-oa)
Funders
This work was supported through a research contract with the lead author (RCC) funded by the Canadian Centre on Substance Use and Addiction using Health Canada Cannabis Research Initiative funds. (Not applicable)
Topics
  • Health Sciences › Medicine › Pharmacology › Cannabis and Cannabinoid Research
  • Health Sciences › Medicine › Psychiatry and Mental health › Schizophrenia research and treatment
  • Health Sciences › Medicine › Epidemiology › Substance Abuse Treatment and Outcomes
Keywords
cannabis legalization, Cannabis Act, cannabis-induced psychosis, schizophrenia, emergency department presentation, psychosis, amphetamine psychosis, alcohol-induced psychosis, Ontario, Alberta
MeSH terms
Alberta, Amphetamines, Cannabis, Marijuana Abuse, Emergency Service, Hospital, Humans, Ontario, Psychotic Disorders

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