Trends in non-medical prescription opioids and heroin co-use among adults, 2003-2014

Background: Patterns in non-medical prescription opioid (NMPO) and heroin use have recently shifted, with evidence that NMPO-only users transition to NMPO and heroin co-use. Co-use is associated with increased risk of morbidity and overdose, highlighting the need for further investigation. This study aims to quantify, describe, and explore trends in co-use. Methods: Using data from the 2003-2014 National Surveys on Drug Use and Health, we compared co-use to NMPO- and heroin-only use across demographic, substance use and mental health characteristics with chi-squared tests. Logistic regression models assessed trends in opioid use overall, and among co-users. Results: From 2003 to 2014, the prevalence of all opioid use (NMPO-only, heroin-only, and co-use) and NMPO-only use decreased 6.08% (p < 0.01) and 4.65% (p < 0.001), respectively, while prevalence of heroin-only use increased 21.32% (non-significant). Co-use increased 248.17% (p < 0.001) overall, and did so in all demographic, substance use, and mental health groups. Demographic, substance use, and mental health characteristics of co-users were more similar to the heroin-only group than to NMPO-only. The highest co-use prevalence was among those: without health insurance (8.72%), aged 26-34 (9.76%), reporting unemployment (12.08%), and with a major depressive episode, psychological distress, and who illicitly use or abuse drugs other than opioids or marijuana in the past year (9.33%, 10.75%, 11.87%, and 16.81%, respectively). Discussion: The increased prevalence of co-use and differences across demographic, substance use, and mental health characteristics highlight the need for targeted prevention and response interventions for this emerging, high-risk group.