Heavy cannabis users at elevated risk of stroke: evidence from a general population survey

Objective: Case reports and hospital-based case-control studies suggest that cannabis use may increase the risk of stroke. We examined the risk of non-fatal stroke or transient ischemic attack (TIA) among cannabis users in the general community. Method: A general population survey of Australians aged 20-24 years (n= 2,383), 40-44 years (n= 2,525) and 60-64 years (n= 2,547) was used to determine the odds of lifetime stroke or TIA among participants who had smoked cannabis in the past year while adjusting for other stroke risk factors. Results: There were 153 stroke/TIA cases (2.1%). After adjusting for age cohort, past year cannabis users (n= 1,043) had 3.3 times the rate of stroke/TIA (95% CI 1.8-6.3, p< 0.001). The incidence rate ratio (IRR) reduced to 2.3 after adjustment for covariates related to stroke, including tobacco smoking (95% CI 1.1-4.5). Elevated stroke/TIA was specific to participants who used cannabis weekly or more often (IRR 4.7, 95% CI 2.1-10.7) with no elevation among participants who used cannabis less often. Conclusions: Heavy cannabis users in the general community have a higher rate of non-fatal stroke or transient ischemic attack than non-cannabis users.