Exploring the Role of Reward Functioning in the Overlap of Post-Traumatic Stress and Cocaine Use Disorder.

backgroundPosttraumatic stress disorder (PTSD) symptoms are common in people with cocaine use disorder (CUD), and even sub-threshold PSTD symptoms result in worse treatment outcomes. Difficulties with reward functioning may drive this comorbidity. Impairments in reward functioning are prominent in both PTSD and CUD and contribute to development of substance use problems after trauma. There are three distinct reward processes that may be involved in the PTSD/CUD overlap: consummatory reward (ability to experience pleasure), motivational reward (willingness to exert effort for rewards), and reward learning (adapting behavior based on reward history). Here we test whether impairments in these reward functions account for the relationship between PTSD and CUD symptoms.

methodsThis is a secondary analysis of data from a clinical trial (NCT02773212) that measured of PTSD symptoms, CUD severity, consummatory reward, motivational reward, and reward learning in 53 treatment-seeking people with CUD.

resultsGreater PTSD symptoms related to (1) more severe CUD and (2) less ability to learn from reward; however, impaired reward learning did not significantly account for the overlap in PTSD and CUD symptom severity.

conclusionsThe observed relationship between PTSD and CUD symptoms was not accounted for by reduced ability to experience pleasure from rewards, reduced motivation for rewards, or reduced ability to learn from rewards. Thus, treatments that attempt to enhance reward functioning seem unlikely to address this complex comorbidity.