A national population-based study of cannabis use and correlates among U.S. veterans prescribed opioids in primary care

BACKGROUND: Cannabis is marketed as a treatment for pain. There is limited data on the prevalence of cannabis use and its correlates among Veterans prescribed opioids. OBJECTIVE: To examine the prevalence and correlates of cannabis use among Veterans prescribed opioids. DESIGN: Cross-sectional study. PARTICIPANTS: Veterans with a urine drug test (UDT) from Primary Care 2014–2018, in 50 states, Washington, D.C., and Puerto Rico. A total of 1,182,779 patients were identified with an opioid prescription within 90 days prior to UDT. MAIN MEASURES: Annual prevalence of cannabis positive UDT by state. We used multivariable logistic regression to assess associations of demographic factors, mental health conditions, substance use disorders, and pain diagnoses with cannabis positive UDT. RESULTS: Annual prevalence of cannabis positive UDT ranged from 8.5% to 9.7% during the study period, and in 2018 was 18.15% in Washington, D.C. and 10 states with legalized medical and recreational cannabis, 6.1% in Puerto Rico and 25 states with legalized medical cannabis, and 4.5% in non-legal states. Younger age, male sex, being unmarried, and marginal housing were associated with use (p < 0.001). Post-traumatic stress disorder (adjusted odds ratio [AOR] 1.17; 95% confidence interval [CI] 1.13–1.22, p < 0.001), opioid use disorder (AOR 1.14; CI 1.07–1.22, p < 0.001), alcohol use disorder or positive AUDIT-C (AOR 1.34; 95% CI 1.28–1.39, p < 0.001), smoking (AOR 2.58; 95% CI 2.49–2.66, p < 0.001), and other drug use disorders (AOR 1.15; 95% CI 1.03–1.29, p = 0.02) were associated with cannabis use. Positive UDT for amphetamines AOR 1.41; 95% CI 1.26–1.58, p < 0.001), benzodiazepines (AOR 1.41; 95% CI 1.31–1.51, p < 0.001) and cocaine (AOR 2.04; 95% CI 1.75–2.36, p < 0.001) were associated with cannabis positive UDT. CONCLUSIONS: Cannabis use among Veterans prescribed opioids varied by state and by legalization status. Veterans with PTSD and substance use disorders were more likely to have cannabis positive UDT. Opioid-prescribed Veterans using cannabis may benefit from screening for these conditions, referral to treatment, and attention to opioid safety. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12888-023-04648-5.