Canada's Post-Legalization Adverse Reaction Reports Reveal Patterns in Cannabis Side Effects

Among 698 adverse reaction reports to the Canada Vigilance Program, the average reporting individual was 56 years old, 45.4% were female, and 67.5% reported medical use (mainly pain management). Most cases (62.3%) were reported as serious, and 68.8% involved cannabis extracts. THC-dominant products were associated with different side effect profiles than CBD-dominant products. Common adverse events included hallucination, headache, nausea, dizziness, and dyspnea.

Descriptive analysis of spontaneous adverse reaction reports submitted to Canada's post-market surveillance system since cannabis legalization in October 2018. Each case was assessed for causality. Data were aggregated to identify demographic patterns, product types involved, and event frequencies. Reports were from the Canada Vigilance Program's standardized pharmacovigilance framework.

Canada's legalization framework included pharmaceutical-grade post-market surveillance for cannabis, making this the first large-scale adverse reaction reporting dataset from a legal regulated market. The data reveal that most reports come from older medical users of cannabis extracts, not recreational users, and that product composition matters for side effect profiles.

Spontaneous reporting systems capture only a fraction of actual adverse events, but they can identify emerging safety signals. The predominance of older medical users in these reports may reflect both this population's higher engagement with healthcare and greater vulnerability to side effects, rather than indicating recreational products are safer.

Spontaneous reporting captures a small fraction of actual adverse events. Reports are subject to reporting bias. "Serious" classification includes "other medically important condition," which may not always reflect clinical severity. Cannot determine adverse event rates or compare to overall user population.