Whether cannabis increases the risk of blood clots has remained unclear until now. A new analysis covering ten years finds no such connection. What makes this particularly noteworthy is that we reported the opposite four years ago.
The Journal of Cannabis Research has published a retrospective cohort study investigating whether cannabis use disorder is associated with venous thromboembolism—that is, blood clots in deep veins and pulmonary embolism. The study is based on the TriNetX US Collaborative Network, a database of electronic patient records.
How the Analysis Was Conducted
No association was found. The risk ratio for venous thromboembolism was 1.01, with a confidence interval ranging from 0.85 to 1.21. For deep vein thrombosis alone, the ratio was 1.06, and for pulmonary embolism, 0.97. A value of 1.0 indicates the groups do not differ, and the confidence interval rules out any meaningful effect in either direction.
The authors varied their calculations further, testing different follow-up periods and different definitions of exposure, and incorporated positive controls. This is the component that makes such research robust: if a method detects known associations but fails to find the one under investigation, that argues against the association itself rather than the methodology.
Why This Matters to Us
In 2022, we reported on elevated thrombosis risk among cannabis smokers. This new work contradicts that finding for the population studied. This is not a contradiction in the sense of error, but rather the normal course of science: early signals came predominantly from clinical settings, trauma and surgical cohorts, and findings were inconsistent. The study cites this very discrepancy as its motivation.
What cannot be concluded from this: any statement about occasional use. The study examined a diagnosed use disorder—a clinically significant pattern of consumption. And it examined a US population with US healthcare data.
Null findings like this rarely make headlines, even though they often provide the more useful information for patients. The same applies to predictions of increased consumption following Germany’s legalization, which a survey of 35,957 individuals did not support.
Source: Mu H. et al., „Cannabis use disorder and risk of venous thromboembolism: a retrospective cohort study“, Journal of Cannabis Research, October 19, 2026, DOI 10.1186/s42238-026-00520-x. This article does not replace medical advice.
Verfolgst du Studien zu möglichen Risiken von Cannabis?
Branchen-Update
News, Analysen und Reportagen — mehrmals im Monat direkt in dein Postfach.
