Substance-Related and Addictive Disorders

Substance-related and addictive disorders have played a central role throughout the four decades of the HIV epidemic. The use of opioids and other drugs by injection has been a vector for direct transmission, while the alignment of substances’ psychoactive properties, substance-related behaviors and social networks, and associated social and structural conditions contributed to unchanging, high rates of new HIV infections for many years. Recent advances in HIV prevention have made the United States’ strategic plan to end the HIV epidemic a realistic goal. Achievement of the plan’s ambitious targets depends on reaching vulnerable marginalized individuals who are either at risk for or living with HIV. Individuals who use substances have historically been difficult to engage and retain in medical care. The additional burden of HIV infection has raised the stakes and urgency to connect with vulnerable persons with addictive disorders and link them to HIV prevention efforts or HIV and addiction treatment services. This chapter begins with a brief overview of substance use as a driver of the HIV epidemic and the epidemiology of substance-related disorders and HIV. The substances that are catalysts of the epidemic include alcohol, marijuana, opioids, cocaine, crack cocaine, club drugs, methamphetamine, and novel psychoactive substances. The importance of early detection and engagement in care, and methods of identification of specific substances are discussed. The interplay between substance use and other social and behavioral factors is believed to intensify substances’ negative impact on HIV burden and outcomes. Substance-related sexual behaviors, stigma, trauma, violence, and psychiatric comorbidity are described. The substances most commonly associated with HIV are reviewed in detail, including prevalence, role in HIV acquisition, and effect on HIV disease progression. Assessment and management of substance-related disorders and corresponding drug-drug interactions between antiretrovirals and medications used to treat the disorders are discussed.