Importance: Cannabis has been proposed as a therapeutic with potential opioid-sparing properties in chronic pain, and its use could theoretically be associated with decreased amounts of opioids used and decreased risk of mortality among individuals prescribed opioids.

Question: Is cannabis use associated with increased risk of mortality among patients prescribed opioid analgesics?

Findings: In this cohort study among 297 620 patients in the Veterans Affairs health system treated with opioids in the prior 90 days, cannabis use was not associated with increased mortality among participants aged less than 65 years, but was associated with increased 90-day mortality among those aged 65 years and older receiving long-term opioid therapy. No increase in mortality was found at 180 days.

Meaning: This study found that cannabis use was associated with increased short-term mortality risk among adults aged 65 years and older receiving long-term prescription opioids.