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Study breakdown

People who visited the ER for cannabis had nearly four times the risk of developing an anxiety disorder

Retrospective CohortStrong evidence
The takeaway

Among 12 million Ontarians, those with a cannabis-related ER visit had a 3.7-fold increased risk of anxiety disorder diagnosis within three years, with young males at highest risk (5.7x).

Emergency physicians, psychiatrists, public health policymakers, and individuals who have experienced cannabis-related distress.

What the researchers found

Within 3 years of a cannabis ER visit, 12.3% were diagnosed with anxiety (ED/hospital) vs 1.2% general population (aHR 3.69). Including outpatient: 23.6% vs 5.6% (aHR 3.88). Young males: aHR 5.67. Young females: aHR 3.22.

Why it matters

Cannabis-related ER visits may identify individuals at very high risk for developing anxiety disorders, offering a clinical window for screening and intervention.

The numbers in context

12,099,144 individuals. 34,822 cannabis ER visits. 3-year anxiety: 12.3% vs 1.2%. aHR 3.69. Young males: aHR 5.67.

How the study worked

Population-based cohort using Ontario administrative data (2008-2019). 12,099,144 individuals without prior anxiety. 34,822 had cannabis ER visits. Cause-specific hazard models.

What this study cannot tell us

Cannot determine causation. ER visits represent the most severe reactions. Cannot measure use patterns or potency.

How to read the evidence

Massive population cohort (12 million) with appropriate hazard modeling. Cannot determine causation.

When this study was published

2024 publication using 2008-2019 data.

The bigger picture

Cannabis ER visits are increasing with legalization. If these visits represent high-risk moments, they offer opportunities for brief intervention that could prevent chronic anxiety.

Questions still open

  • Would anxiety screening after cannabis ER visits reduce disorder development?
  • Is the association driven by cannabis causing anxiety or shared vulnerabilities?

Common questions

Does cannabis cause anxiety disorders?
This study found a strong association but cannot prove causation. People prone to anxiety may have stronger adverse reactions to cannabis. The relationship likely runs in both directions.
Why are young males at highest risk?
Young males had 5.7x relative risk, possibly reflecting higher-potency use, biological vulnerability during brain development, or lower baseline anxiety diagnosis rates.

Read the original research

Development of an anxiety disorder following an emergency department visit due to cannabis use: a population-based cohort study.

EClinicalMedicine, 69, 102455

Citation

Myran, Daniel T; Harrison, Lyndsay D; Pugliese, Michael; Tanuseputro, Peter; Gaudreault, Adrienne; Fiedorowicz, Jess G; Solmi, Marco. (2024). Development of an anxiety disorder following an emergency department visit due to cannabis use: a population-based cohort study.. EClinicalMedicine, 69, 102455. https://doi.org/10.1016/j.eclinm.2024.102455

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