Prescription Opioid and Marijuana Use on an American Indian Reservation: Comorbid Versus Marijuana Use Only

Background: Non-medical use of prescription opioid pain relievers (OPR) is a significant public health problem in the United States with approximately 2.1 million Americans experiencing OPR-related substance use disorders. OPR-related problems have been rising for 15 years, documented by exponential increases in OPR-related mortalities and emergency department visits. Over the same time period, the national political climate is becoming more favorable for marijuana decriminalization, with some States and American Indian reservations legalizing it. With decriminalization/legalization, use will likely increase making comorbidity of marijuana and other drugs increasingly relevant to researchers, practitioners, and policy makers. Of particular concern are American Indians/Alaska Natives (AI/AN) who experience the highest rates of OPR use (tied with Whites) and marijuana use, yet very little empirical literature is published on these topics with AI/ANs. The present study investigates demographic and behavioral differences among lifetime comorbid marijuana and OPR users versus those with lifetime marijuana use alone in a population of reservation-based AI/ANs.

 Methods: Data are from a self-report questionnaire administered to 400 adult (ages 18+) tribal members of a Midwest reservation. A convenience sampling design was developed based on tribal input recruiting participants from popular local venues. Substance use questions were based on questions from national surveys, including the Drug Abuse Screening Test-10 to measure drug-related problems. Data were analyzed with bivariate statistics and multinomial logistic regression to generate Odds Ratios (OR) contrasting lifetime marijuana use alone and comorbid lifetime marijuana and OPR (defined as OxyContin and/or Vicodin use).

 Results: Among the 362 surveys with complete data, 23.3% of participants never used OPR or marijuana, 40% used marijuana but never OPR, and 35.3% used OPR and marijuana. Considerable comorbidity was found between OPR and marijuana with only 7 participants reporting having used OPR but never marijuana. Compared to ages 18-24, older individuals were significantly less likely to have used marijuana or OPR (OR: 4.5 for ages 26-24; OR: 53.2 for ages >50) and more likely to have used only marijuana (OR: 3.2 for ages 35-49; OR: 14.6 for ages >50) in their lifetimes. Significantly more comorbid users had sought treatment for drug use (66.7%; p<0.001) and reported more drug-related problems (mean=3.3; p<0.001) than participants with only marijuana use. 

Conclusions & Implications: The high rate of lifetime OPR use in this sample is alarming. Comorbid users have significantly more drug-related problems and are more likely to have sought treatment than participants who use marijuana alone. This suggests using multiple drugs inflates risk for negative drug-related outcomes among this sample of AI/ANs. Marijuana only users are older whereas comorbid users are younger, highlighting the need for OPR-prevention programs targeting youth. As marijuana legislation becomes more relaxed, researchers and practitioners will need to pay greater attention to comorbid use of marijuana among OPR users. It will be beneficial to increase knowledge on interaction effects of comorbid use as they may impact drug-related behaviors and outcomes.