Aims:

Cannabis use has been reported as a risk factor for stroke. We systematically review the prevalence and outcomes of stroke in people with cannabis use.

Methods:

We searched MEDLINE and 6 other databases from inception to January 2020 for studies on the relationship between cannabis use and stroke. We followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) recommendations. Two independent reviewers extracted the data. Study quality was assessed by the Newcastle-Ottawa Scale for cohort and case-control studies.

Results:

Seventeen studies involving 3,185,560 people with cannabis use were included. Descriptive statistics demonstrated 18,676 (median 1.1%, interquartile range [IQR] 0.3%–1.3%) experienced stroke compared with 0.8% of those without use (Odds Ratio 1.17, 95% CI 1.10–1.25). Among people with cannabis use, median age was 26.2 years (IQR 25.2–34.3 years) and mostly male (median 57.8%). Of stroke subtypes, ischemic stroke was most prevalent (median 1.2%, IQR 0.4%–1.9%), followed by undefined stroke subtype (median 1.2%, IQR 1.1%–1.2%) and hemorrhagic stroke (median 0.3%, IQR 0.1%–0.6%). The majority of people with cannabis use who experienced stroke survived (median: 85.1%, IQR 83%–87.5%) and 64.0% of people experienced a good neurologic outcome, defined as modified Rankin Scale of 0 to 3. Few studies included outcomes of vasospasm or seizure.

Conclusions:

In people with cannabis use, the prevalence of ischemic stroke and hemorrhagic stroke was 1.2% and 0.3%, respectively, higher than the prevalence of people without use (0.8% and 0.2%). There is insufficient information on timing, exposure, duration, and dose-responsive relationship.