Cannabis and Heart Attack/Stroke Risk: A 183-Million-Patient Meta-Analysis Finds Stroke Risk but Not Heart Attack Risk

Systematic review and meta-analysis of 20 observational studies including 183,410,651 patients. Searched PubMed, Scopus, and Cochrane Library databases. Data on effect estimates combined via random-effects meta-analysis using the DerSimonian and Laird method with generic inverse-variance strategy. Outcomes: acute myocardial infarction and stroke.

This is the largest meta-analysis of cannabis and cardiovascular risk ever conducted. With over 183 million patients, it has statistical power that individual studies lack. The finding that stroke risk is elevated while heart attack risk is not suggests cannabis may affect the cardiovascular system in specific ways — possibly through effects on blood vessel function, blood pressure regulation, or clotting — rather than through a general increase in cardiovascular disease.

Cardiovascular safety is one of the most important outstanding questions in cannabis research, especially as use increases among middle-aged and older adults. This meta-analysis provides the strongest evidence to date that stroke risk warrants attention, while partially alleviating heart attack concerns. For the RethinkTHC database, this connects to the broader harm-reduction narrative — legalization brings both increased access and a need for better safety data.

All included studies were observational — the association between cannabis and stroke cannot be confirmed as causal. Residual confounding is a major concern: cannabis users may differ from non-users in smoking habits, other drug use, and socioeconomic factors that independently affect cardiovascular risk. The definition of 'cannabis use' varied across studies (current vs. ever, frequency, route of administration). The very low proportion of males (23.7%) in the overall sample is unusual and may reflect specific study populations. Publication bias is possible.