Identifying risk factors for marijuana use among veterans affairs patients

Cannabis is the most widely used drug in the United States, and its use carries negative health consequences; however, universal screening for cannabis use is cumbersome. If data commonly collected in the primary care setting (eg, use of alcohol, smoking status, and depression symptoms) could predict cannabis use, then providers can implement targeted marijuana screening in high-risk groups.

We reviewed Behavioral Health Laboratory data collected between 2003 and 2006 from 5512 patients referred by Veterans Affairs primary care clinics for potential mental health needs. Logistic regression was used to determine the predictors of past year marijuana use.

A total of 11.5% of the sample reported using marijuana in the past year. Age, gender, other drug use, presence of alcohol use disorders, smoking status, depressive disorders, posttraumatic stress disorder, anxiety disorders, and psychotic symptoms, individually, were associated with the patients' use of marijuana during the past year. When controlling for age, race, and gender in a logistic regression analyses, only other drug use, alcohol use disorder, and smoking status were linked to past year marijuana use. Patients were 5.4 (95% confidence interval [CI] 4.3-6.7) times more likely to have used marijuana during the past year if they used another illicit drug during the past year. Those with alcohol use disorder diagnosis or current smokers were 2.3 (95% CI 1.9-2.8) and 1.5 times (95% CI 1.3-1.7), respectively, more likely to have used marijuana during the past year. Receiver operating characteristic curve (area under curve = 0.79) represents good sensitivity and specificity of the model, correctly classifying 88.4% of the past year marijuana users.

Identifying patients at high risk for cannabis use may facilitate targeted screening and provision of interventions in primary care. Patients who screen positive for cigarette use, alcohol abuse or dependence, or have evidence of other illicit drug use could be considered for cannabis screening.