Cannabis use before first psychiatric hospitalization rose from 17% to 26% in Ontario over a decade

What the researchers found

Cannabis use within 30 days of first psychiatric admission rose from 16.7% in 2007 to 25.9% in 2017. Cannabis use disorders increased from 3.8% to 6.0%. In 2017, 47.9% of patients aged 18-24 and 39.2% aged 25-34 used cannabis before admission. The largest diagnostic-group increases were in personality disorders (15% increase), schizophrenia/psychotic disorders (14%), and substance use disorders (14%).

Why it matters

This decade-long population-level trend data from an entire province establishes a clear baseline showing rising cannabis use among psychiatric inpatients. As a pre-legalization baseline (Canada legalized in 2018), it enables future assessment of whether legalization accelerated these trends.

The numbers in context

81,809 first admissions; 20.1% used cannabis overall; 16.7% in 2007 to 25.9% in 2017; CUD 3.8% to 6.0%; 47.9% of 18-24 year olds in 2017; AUC 0.88 for schizophrenia-gender interaction model

How the study worked

Retrospective cross-sectional analysis of 81,809 first-time admissions to non-forensic inpatient psychiatric beds in Ontario from 2007-2017 using the Ontario Mental Health Reporting System. Trends and characteristics were analyzed across years and diagnostic categories.

What this study cannot tell us

Cannot determine whether cannabis use contributed to psychiatric admission or was incidental. Self-reported use may undercount actual use. Ontario-specific data. No post-legalization comparison.

How to read the evidence

Province-wide administrative data covering over 81,000 first admissions across a decade, though administrative data cannot establish causation.

When this study was published

Published in 2021 using data from 2007-2017.

The bigger picture

Nearly half of young adult first-time psychiatric inpatients used cannabis before admission by 2017. Whether cannabis contributes to psychiatric crises or people in psychiatric distress are more likely to use cannabis remains a critical unanswered question.

Questions still open

• Did legalization in 2018 accelerate these trends? Is the increase driven by higher-potency products? Would screening and brief intervention for cannabis use in psychiatric settings improve outcomes? How does concurrent cannabis use affect treatment response?

Common questions

Read the original research

How High? Trends in Cannabis Use Prior to First Admission to Inpatient Psychiatry in Ontario, Canada, between 2007 and 2017.

Canadian journal of psychiatry. Revue canadienne de psychiatrie, 66(12), 1059-1068

Citation

McGuckin, Taylor; Ferro, Mark A; Hammond, David; Stewart, Shannon; Maloney-Hall, Bridget; Madi, Nawaf; Porath, Amy; Perlman, Christopher M. (2021). How High? Trends in Cannabis Use Prior to First Admission to Inpatient Psychiatry in Ontario, Canada, between 2007 and 2017.. Canadian journal of psychiatry. Revue canadienne de psychiatrie, 66(12), 1059-1068. https://doi.org/10.1177/0706743720984679

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