Comorbidities of substance use: Opportunities realized and future needs

Over the past two decades, the National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN) has made major contributions to progress in substance use treatment research. However, contributions to research addressing the considerable medical and mental health comorbidities of substance use, which can impede treatment efficacy and compromise health, have been emphasized less. In this Commentary, we review the contributions of CTN studies focused on medical comorbidities, initially centered on the HIV epidemic in people who use drugs, and subsequently broadened to address hepatitis C and life-threatening bacterial infections; as well as mental health comorbidities, especially post-traumatic stress disorder, attention-deficit/hyperactivity disorder, and suicidality. These studies demonstrate that comorbidities assessments and treatment can be feasibly implemented in substance use treatment programs and, conversely, that substance use assessments and treatments can be feasibly implemented in clinical care sites. We highlight the NIDA CTN Data Share as an invaluable resource for secondary analyses of comorbidities using data from CTN substance use treatment protocols and provide examples of its use. We describe the work of the CTN Comorbidities of Substance Use Special Interest Group (SIG), formerly known as the HIV SIG, as an example of the role that SIGs can play in facilitating CTN research in areas of emerging significance. We emphasize the importance of implementing a "whole person" approach-one that integrates both substance use and comorbidities outcomes. We identify promising opportunities for conducting this research by studying strategies for integrating prevention, screening, linkage, treatment, adherence, and retention support for comorbidities into substance use disorder (SUD) treatment venues; as well as strategies for integrating SUD treatment into primary care venues, hospitals, and other non-SUD clinical settings.