Importance: The association between mortality and cannabis use remains unclear.

Question: Is there an association between cannabis use and all-cause, cardiovascular disease (CVD), and cancer mortality?

Findings: In this cohort study of 121 895 participants, in the fully adjusted model among females, the risk for CVD mortality was significantly higher among heavy cannabis users compared with never users; there was no association among males. No association was observed among females or males for all-cause and cancer mortality.

Meaning: The findings suggest that heavy cannabis use is associated with CVD mortality among females.