Mediation of suicide ideation in prolonged exposure therapy for posttraumatic stress disorder

Background: Evidence-based treatments for posttraumatic stress disorder (PTSD) are associated with reduction in suicidal ideation (SI), yet the mechanisms underlying this reduction are unclear. The current study investigated improvements in PTSD, depression, and social support as potential mediators of the change in SI over time. Method: Participants (N = 200) were active duty military personnel with PTSD randomized to prolonged exposure therapy (PE) or present-centered therapy (PCT). Using parallel mediation and serial mediation models, we examined the relative influence of the mediators on suicidal ideation over time. Results: Consistent with our hypotheses, lagged mediation analyses revealed that depression was the strongest mediator of improvements in SI over time in PE and PCT. Reductions in PTSD were associated with subsequent reductions in depression, which was associated with reductions in SI. Treatment condition did not moderate this relationship, and social support was not a significant mediator. Conclusions: In active duty military personnel, reduction in depression was the strongest mediator of reduction in suicidal ideation in PE and PCT for PTSD. These results were not altered by treatment condition. Trial registration: Clinicaltrials. gov identifier: NCT01049516. http://www.clinicaltrials.gov/show/NCT01049516.