What topics does this cannabis study cover?

This study covers research on: Mental Health, THC.

Where was this research published?

Published in Journal of cannabis research on June 10, 2026.

Legalization didn't improve public knowledge of cannabis health risks

Knowledge about the health effects of cannabis before and after legalization of 'recreational' cannabis in Canada: findings from the International Cannabis Policy Study, 2018-2024.

Journal of cannabis research • June 10, 2026 • Moderately Relevant

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AI Summary

This major study tracked public knowledge about cannabis health effects in Canada across 93,933 respondents before and after recreational legalization in 2018-2024. Researchers measured how well Canadians understood seven key health risks, including impaired driving, pregnancy complications, psychosis, and diabetes. The findings reveal a complex picture: while public understanding remained relatively stable overall, specific knowledge gaps emerged and even worsened in some areas after legalization became legal.

The research identified significant disparities in health knowledge across different groups. Non-consumers, youth aged 16-25, and people without mental illness histories demonstrated the highest understanding of cannabis risks. However, frequent cannabis users showed persistent knowledge gaps, particularly regarding mental health risks and pregnancy harms. Most concerning, the study documented declining awareness of several specific harms in the five years following legalization, including risks during pregnancy/breastfeeding, dangers while driving, and the link between cannabis use and psychosis or schizophrenia.

For the general public, agreement on risks varied dramatically: approximately 80% understood impaired driving risks, but only 34-38% recognized the connection to psychosis and schizophrenia—a critical gap given cannabis's documented mental health effects. The findings suggest that legalization alone does not automatically improve public health knowledge, and may even reduce awareness of certain serious risks. These results underscore the need for more targeted, evidence-based public education campaigns, especially for frequent users and vulnerable populations.

📄 Original Abstract

Although prior research has examined how cannabis legal status relates to psychosocial predictors of use, less is known about whether recreational legalization influences public knowledge of specific cannabis-related health effects. This study addresses this gap by analyzing trends in knowledge of health effects of cannabis consumption following the legalization of recreational cannabis in Canada. Data were collected from repeated cross-sectional national surveys conducted in the year prior to legalization of 'recreational' cannabis in Canada (2018), and five years post-legalization (2019-2023) among 93,933 respondents aged 16-65. Regression models examined differences pre vs. post-legalization in health knowledge, assessed as agreement with each of 7 health effects from cannabis and a composite Health Knowledge Index, adjusting for cannabis consumption, mental health history, and sociodemographics. Across all years, agreement was highest for the risks of impaired driving (79-81%) and lowest for psychosis and schizophrenia risk (34-38%). Health knowledge was highest among non-consumers, those without mental illness history, and youth aged 16-25 (p < .001, all contrasts). No changes were observed in the Health Knowledge Index pre vs post-legalization; however, significant decreases were observed for harms during pregnancy or breastfeeding (p < .001), danger while driving or operating machinery (p = 0.015), risk of psychosis and schizophrenia (p = 0.003), and risk of diabetes (p = 0.001). Overall, only modest differences in knowledge of cannabis health effects were observed in the 5 years following cannabis legalization in Canada; however, persistent gaps in health knowledge remained, particularly among frequent consumers.