Comorbidity of Depression and Posttraumatic Stress Disorder: Outcomes From a Randomized Controlled Trial of Surf and Hike Therapies Among Service Members

Objective: Major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) are commonly comorbid mental health disorders. Exercise performed in the natural environment has shown promise in relieving symptoms of each disorder separately; however, the effectiveness has seldom been studied in comorbid populations. Method: Data were derived from a randomized controlled trial of surf and hike therapy for active duty service members with MDD (N = 95). In this study, participants were grouped by comorbidity status (MDD, n = 37; MDD-PTSD, n = 58). Clinician-administered and self-reported measures were completed at preprogram, postprogram, and 3-month follow-up; a brief depression/anxiety measure was completed before and after each session. Results: Multilevel modeling results showed clinically significant decreases in depression severity across participants from pre- to postprogram (p < .001) and within exercise sessions (p < .001), with no further change through follow-up. No significant differences emerged in depression severity change over time by comorbidity status, intervention condition, or their three-way interaction. Those with PTSD showed reductions in posttraumatic stress symptoms from pre- to postprogram (p < .001), which did not differ by intervention condition; gains were maintained at follow-up. Remission rates from MDD and PTSD diagnoses (if applicable) were significant from pre- to postprogram for both MDD-only and MDD-PTSD groups (p < .001). These improvements were maintained at 3 months. Conclusions: Both surf and hike therapies can improve MDD and PTSD symptoms, regardless of comorbidity status, suggesting utility of these interventions among service members with one or both disorders.