Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Epidemiology and Biostatistics

Supervisor

Anderson, Kelly K.

Abstract

The legalization of non-medical cannabis has raised concerns regarding potential impacts on psychotic disorders. The objective of this thesis was to investigate the population-level effects of non-medical cannabis legalization on psychotic disorders. The findings from our scoping review suggest that as the non-medical cannabis retail market expanded, increases in health service use for psychotic disorders were observed; however, no changes were observed during a time of market restrictions. We then conducted an ecological study, which found quarterly regional cannabis sales per capita was correlated with quarterly prevalence of emergency department visits and hospitalizations for psychotic disorders. These findings suggest that the expansion of the non-medical cannabis market may lead to increases in health service use for psychotic disorders. Further research is needed to understand the mental health implications of cannabis legalization and whether policy changes need to be made to cannabis product availability and resourcing of mental health services.

Summary for Lay Audience

Psychotic disorders, such as schizophrenia and bipolar disorder, are a group of mental illnesses that affect brain function by altering thoughts, beliefs, and perceptions. Symptoms of psychosis include delusions, hallucinations, and disorganized thought and speech. One known risk factor for psychosis is cannabis, which has been linked to triggering psychotic episodes and making symptoms worse for those with existing psychotic disorders.

In October 2018, Canada became the second country to legalize cannabis; the impacts of legalization on psychotic disorders are yet to be determined. Our first study used a scoping review approach to compile the findings from fourteen research studies that examined the impacts of cannabis legalization on health service use for psychotic disorders in Canada and the United States. We found that as the cannabis market expanded, there were corresponding increases in health service use for psychotic disorders. Our second study examined the association between regional cannabis sales and the use of acute mental health services for psychotic disorders in Ontario. We used health administrative data and cannabis sales data to examine whether regions with higher total sales also had a higher frequency of psychosis-related emergency department visits and hospitalizations. We found that between October 2018 and March 2022, quarterly regional cannabis sales per capita was correlated with health service use for psychotic disorders.

These findings will provide information on the population-level impacts of cannabis legalization on mental health resources in Ontario. More studies are needed as the cannabis retail market expands across Canada to evaluate the population-level impact of cannabis legalization on psychotic disorders.

Available for download on Saturday, May 17, 2025

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Epidemiology Commons

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