Background and Purpose - Current knowledge on cannabis use in relation to stroke is based almost exclusively on clinical reports. By using a population-based cohort, we aimed to find out whether there was an association between cannabis use and early-onset stroke, when accounting for the use of tobacco and alcohol.

Methods - The cohort comprises 49321 Swedish men, born between 1949 and 1951, who were conscripted into compulsory military service between the ages of 18 and 20. All men answered 2 detailed questionnaires at conscription and were subject to examinations of physical aptitude, psychological functioning, and medical status. Information on stroke events up to approximate to 60 years of age was obtained from national databases; this includes strokes experienced before 45 years of age.

Results - No associations between cannabis use in young adulthood and strokes experienced 45 years of age or beyond were found in multivariable models: cannabis use >50 times, hazard ratios=0.93 (95% confidence interval [CI], 0.34-2.57) and 0.95 (95% CI, 0.59-1.53). Although an almost doubled risk of ischemic stroke was observed in those with cannabis use >50 times, this risk was attenuated when adjusted for tobacco usage: hazards ratio=1.47 (95% CI, 0.83-2.56). Smoking 20 cigarettes per day was clearly associated both with strokes before 45 years of age, hazards ratio=5.04 (95% CI, 2.80-9.06), and with strokes throughout the follow-up, hazards ratio=2.15 (95% CI, 1.61-2.88).

Conclusions - We found no evident association between cannabis use in young adulthood and stroke, including strokes before 45 years of age. Tobacco smoking, however, showed a clear, dose-response shaped association with stroke.