Mediators of the Relationship between Depression and Medication Adherence among HIV Positive Substance Users

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Medication adherence is of utmost importance in predicting health outcomes across numerous chronic conditions, particularly HIV/AIDS. Highly active antiretroviral therapy (HAART) to treat HIV/AIDS requires high levels of adherence to maintain viral suppression, which is crucial for optimal HIV treatment and prevention. One of the most significant patient-level barriers to medication adherence is depressive symptoms. Even at subclinical levels, depressive symptoms predict nonadherence above and beyond other relevant psychosocial factors. Despite the focus on depressive symptoms as a reliable and powerful predictor of nonadherence, few studies have sought to test potential mechanisms underlying this relationship, which is an important step to advance our understanding of how depression affects adherence to inform intervention efforts. The current study utilized early behavioral theories of depression (Lewinsohn, 1974; Ferster, 1973) to select potential mediators that may be relevant to both depression and adherence. Specifically, we tested the key components of these models, (1) goal-directed activation, (2) positive reinforcement, and (3) punishment in one's environment as potential mediators of the relationship between depressive symptoms and medication adherence among HIV positive individuals in substance abuse treatment (n = 73). We examined adherence to HAART as well as adherence to other daily medications using a combination of self-report assessments (% of doses missed over past four days, frequency of doses missed across common reasons for nonadherence) and viral load. Greater levels of punishment mediated a positive relationship between clinician-rated depressive symptoms and greater frequency of missed doses across common reasons for nonadherence. Activation and positive reinforcement were unrelated to adherence or viral load in this sample. Findings suggest the importance of punishment in explaining the relationship between depression and medication nonadherence. Individuals with elevated depressive symptoms may perceive greater negative consequences related to medications (e.g., side effects, stigma) and may be less likely to overcome barriers necessary for optimal adherence. If findings continue to replicate, this may suggest a need to target punishment in HIV prevention and treatment, for instance in the context of integrated cognitive behavior therapy interventions that target depression and adherence among substance users.