Cannabis Poisoning and Mental Health Crises Were Rare Among Medical Cannabis Patients in Ontario
Among 23,091 medically authorized cannabis patients in Ontario, cannabis poisoning-related ER visits occurred at a rate of 8 per 10,000 person-years and cannabis-related mental health ER visits at 15 per 10,000 person-years, with prior substance use and mental health disorders being the strongest predictors.
Quick Facts
What This Study Found
During a median follow-up of 240 days, only 14 patients visited the ER or were hospitalized for cannabis poisoning (8.06 per 10,000 person-years) and 26 for cannabis-related mental and behavioral disorders (15.0 per 10,000 person-years). Predictors of cannabis-related mental health events included prior substance use disorders, other mental disorders, age, diabetes, and COPD.
Key Numbers
23,091 patients; median 240 days follow-up; 14 cannabis poisoning ER visits (8.06/10,000 person-years); 26 mental/behavioral disorder ER visits (15.0/10,000 person-years); prior substance use disorders strongest predictor
How They Did This
Retrospective cohort study of patients who received medical cannabis authorization in Ontario, Canada between 2014-2017. Data from participating cannabis clinics linked to health administrative data. Cox proportional hazard regressions used to identify predictors.
Why This Research Matters
As medical cannabis programs expand, quantifying the rate of acute harms helps patients and clinicians weigh risks. The low overall rates of poisoning and mental health crises in this medically supervised population are reassuring, while the identified risk factors can guide monitoring.
The Bigger Picture
These findings suggest that medical cannabis, when used under clinical authorization, carries a low rate of acute serious harms. However, patients with pre-existing substance use or mental health disorders face higher risk and may need closer monitoring.
What This Study Doesn't Tell Us
Retrospective design with clinic-collected data may miss patients who sought care elsewhere. Short median follow-up of 240 days may underestimate long-term risks. No control group for comparison. Only captures events severe enough to prompt ER visit or hospitalization.
Questions This Raises
- ?How do these rates compare to non-medical cannabis users?
- ?Would longer follow-up reveal increasing rates over time?
- ?Could pre-authorization screening for risk factors reduce acute events?
Trust & Context
- Key Stat:
- 23,091 patients, low event rates
- Evidence Grade:
- Large retrospective cohort with clinical data, but no control group and short follow-up period
- Study Age:
- 2022 study
- Original Title:
- Incidence and Predictors of Cannabis-Related Poisoning and Mental and Behavioral Disorders among Patients with Medical Cannabis Authorization: A Cohort Study.
- Published In:
- Substance use & misuse, 57(10), 1633-1641 (2022)
- Authors:
- Zongo, Arsene(7), Lee, Cerina(7), Dyck, Jason R B(10), El-Mourad, Jihane, Hyshka, Elaine, Hanlon, John G, Eurich, Dean T
- Database ID:
- RTHC-04336
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
How safe is medical cannabis for authorized patients?
In this study, acute harms requiring ER visits were rare: about 8 per 10,000 person-years for poisoning and 15 per 10,000 for mental health crises. However, patients with prior substance use or mental health disorders faced higher risk.
Who is most at risk for problems with medical cannabis?
The strongest predictors were prior substance use disorders and other mental health disorders. Age, diabetes, and COPD were also associated with higher risk of cannabis-related mental health events.
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Cite This Study
https://rethinkthc.com/research/RTHC-04336APA
Zongo, Arsene; Lee, Cerina; Dyck, Jason R B; El-Mourad, Jihane; Hyshka, Elaine; Hanlon, John G; Eurich, Dean T. (2022). Incidence and Predictors of Cannabis-Related Poisoning and Mental and Behavioral Disorders among Patients with Medical Cannabis Authorization: A Cohort Study.. Substance use & misuse, 57(10), 1633-1641. https://doi.org/10.1080/10826084.2022.2102193
MLA
Zongo, Arsene, et al. "Incidence and Predictors of Cannabis-Related Poisoning and Mental and Behavioral Disorders among Patients with Medical Cannabis Authorization: A Cohort Study.." Substance use & misuse, 2022. https://doi.org/10.1080/10826084.2022.2102193
RethinkTHC
RethinkTHC Research Database. "Incidence and Predictors of Cannabis-Related Poisoning and M..." RTHC-04336. Retrieved from https://rethinkthc.com/research/zongo-2022-incidence-and-predictors-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.