Major Depressive Disorder and PTSD Treatment Outcome in Interpersonal Psychotherapy and Prolonged Exposure

Objective: Trauma-focused psychotherapies are first-line treatments for posttraumatic stress disorder (PTSD). For veterans, however, response rates are low, and dropout tends to be high. Some evidence suggests that those with comorbid depression are less likely to complete treatment and improve less in trauma-focused treatments. This study examined treatment noncompletion and PTSD symptom outcomes among veterans with and without comorbid major depressive disorder (MDD) treated for PTSD with either a trauma-focused psychotherapy (prolonged exposure [PE]) or a non-trauma-focused psychotherapy (interpersonal psychotherapy [IPT]). We also examined depressive symptoms as an outcome.

Methods: We conducted a secondary analysis of data from a randomized controlled trial comparing PE and IPT for the treatment of PTSD in veterans. Among 109 veterans starting treatment, 30 (52%) of 58 IPT patients and 21 (41%) of 51 PE patients were diagnosed with MDD. Those completing fewer than 8 sessions were considered noncompleters. Outcomes within each treatment and between treatments were compared by MDD status.

Results: There were no differences in noncompletion by MDD status in IPT. In PE, failure to complete was numerically but nonsignificantly higher in those without MDD. MDD was associated with significantly less PTSD symptom improvement in PE (P=.04) but not in IPT at the end of treatment. Findings from a linear model incorporating posttreatment follow-up data, although not statistically significant, were consistent with the end-of-treatment findings. Comparisons between treatments among those with MDD showed partial support for an advantage of IPT for PTSD symptom improvement. There were no differences between the treatments in change in symptoms of depression.

Conclusions: Findings are consistent with prior research showing that depression is associated with less PTSD symptom improvement in PE, a trauma-focused psychotherapy, but does not affect PTSD outcome in IPT. Although in need of replication in studies designed and statistically powered to test the role of MDD in PTSD treatment outcome, findings suggest a possible advantage for IPT relative to trauma-focused treatment for PTSD for those with comorbid MDD.

Trial Registration: ClinicalTrials.gov identifier: NCTO2586064.