Delay Discounting In Individuals With Posttraumatic Stress Disorder Who Were Receiving Medications For Opioid Use Disorder: The Effect Of Prolonged Exposure Therapy

Almost all (90%) of individuals with opioid use disorder (OUD) report lifetime trauma exposure and 18% meet criteria for posttraumatic stress disorder (PTSD). Delay discounting (DD) is a behavioral economic index of preference for smaller immediate over larger delayed rewards that may underlie these co-occurring conditions. Despite the frequent co-occurrence of PTSD and OUD, research on interventions for DD has primarily targeted those with single conditions, particularly participants with a primary substance use disorder diagnosis. Accordingly, it is unclear whether the findings of these studies are applicable to individuals with co-occurring PTSD. Moreover, there have been no studies evaluating the effect of PTSD-focused interventions on DD. The present study utilized data from two completed trials, wherein participants with PTSD who were receiving medications for OUD (MOUD; e.g., buprenorphine or methadone) were randomized to receive: continued MOUD treatment as usual (TAU; n = 23), Prolonged Exposure therapy (PE; n = 24), or PE with financial incentives contingent upon PE session attendance (PE+; n = 25). The aims of this study were to evaluate the effect of PE for reducing DD levels and investigate the association between PTSD severity and DD in individuals with PTSD who were receiving MOUD. DD scores did not change significantly between intake and week 12 for participants in the TAU or PE groups. However, DD scores significantly increased for PE+ participants, t(164) = 2.19, p = .03. Regression analyses did not reveal a significant relationship between PTSD severity and DD at baseline. However, several baseline clinical characteristics were significantly associated with DD (ps < .05) such that men, those with a shorter duration on MOUD, and individuals with less education had higher levels of DD. Overall, these results challenge the conceptualization of PTSD-related avoidance as a preference for smaller, sooner rewards and suggest that patients who engage in PE+ may develop increased sensitivity to reinforcement timing. Future studies of individuals with PTSD receiving MOUD treatment may benefit from evaluating behavioral economic constructs other than DD and should evaluate whether interventions that target substance use are more efficacious than PE for reducing DD.