Mechanisms of symptom reduction in a combined treatment for comorbid posttraumatic stress disorder and alcohol dependence

Objective: To examine the mechanisms of prolonged exposure (PE) and naltrexone (NAL) that underlie symptom reduction among individuals with comorbid posttraumatic stress disorder (PTSD) and alcohol dependence (AD). We hypothesized that (a) reduction in negative cognitions mediates PTSD improvement during PE; (b) reduction in alcohol craving mediates reduction in drinking frequency during NAL treatment; and (c) PTSD improvement mediates reduction in craving and alcohol use during PE. Method: Participants were 159 individuals meeting the DSM-IV diagnosis of PTSD and AD randomly assigned to 1 of 4 conditions: PE + NAL, PE + placebo (PBO), supportive counseling (SC) + NAL; and SC + PBO. All participants received supportive counseling. Results: Lagged multilevel mediational analyses indicated that (a) a reciprocal relationship between cognitive change and PTSD improvement was observed in PE + NAL, PE + PBO, and SC + NAL, but not in SC + PBO; (b) reduction in craving significantly mediated subsequent decrease in alcohol use in PE + NAL and SC + PBO, but not in PE + PBO and SC + NAL; and (c) PTSD improvement significantly mediated subsequent reduction of craving in PE + PBO, and mediated decrease in alcohol use in PE + NAL. Conclusions: The efficacy of combining PE and NAL for reducing alcohol use among those with comorbid PTSD/AD seems to be through reduction in both PTSD symptoms and craving. These findings shed light on the mechanism of PE and highlight the central role of PTSD in the maintenance of alcohol craving and use in patients with comorbid PTSD/AD.