A randomized controlled trial of surf and hike therapy for U.S. active duty service members with major depressive disorder

Abstract

Background: Major depressive disorder (MDD) is the most prevalent mental health disorder worldwide, including among U.S. service members. In addition to evidence-based treatments, activity-based approaches have been shown to effectively treat depressive symptoms, particularly when they occur in the natural environment.

Methods: This study compared two activity-based interventions, Surf Therapy and Hike Therapy, on depression outcomes among 96 active duty service members with MDD. Participants were randomized to 6 weeks of Surf or Hike Therapy. Clinician-administered and self-report measures were completed at preprogram, postprogram, and 3-month follow-up. A brief depression/anxiety measure was completed before and after each activity session.

Results: Multilevel modeling results showed that continuous depression outcomes changed significantly over time (ps < .001). Although service members in Hike Therapy reported higher average depression scores than those in Surf Therapy, the trajectory of symptom improvement did not significantly differ between groups. Regarding MDD diagnostic status, there were no significant differences between the groups at postprogram (p = .401), but Surf Therapy participants were more likely to remit from MDD than were those in Hike Therapy at the 3-month follow-up (p = .015).

Limitations: The sample consisted of service members, so results may not generalize to other populations. Most participants received concurrent psychotherapy or pharmacotherapy, and, although statistically accounted for, results should be interpreted in this context.

Conclusions: Both Surf and Hike Therapies appear to be effective adjunctive interventions for service members with MDD. Research is needed to examine the effectiveness of these therapies as standalone interventions.

Trial registration: Clinical trials registration number NCT03302611; First registered on 05/10/2017.

Keywords: Depression; Exercise; Military; Natural environment; Nature exposure; Nature-based recreation therapy; Outdoor activity; Physical activity; Randomized controlled trial.

Conflict of interest statement

Spouse of the first author is an employee of Google LLC and has stock options as part of compensation package. Google LLC owns Fitbit products, which were used in the study for secondary data collection. Fitbit data are not reported in the current manuscript. When published, results are not expected to affect the value of the company’s stock. No other authors have any competing interests to report.

© 2023. This is a U.S. government work and not under copyright protection in the U.S; foreign copyright protection may apply.

Figures

Fig. 1

CONSORT flowchart of participants. Intervention “completion,” as determined by the NMCSD Surf and Hike Therapy programs, was defined as completing all but two of the available sessions (up to six sessions) for each modality. The programs were halted due to the COVID-19 pandemic; participants in this cohort (n = 8) were counted neither as completers nor non-completers. Their data were analyzed as intent to treat. Total lost to follow-up is greater than the total number allocated because many participants completed either the postprogram assessment or the follow-up assessment and are thus counted twice. RCT = randomized controlled trial; COVID-19 = coronavirus disease 2019

Fig. 2

Estimated marginal means of MADRS and PHQ-9 at study assessment time points. Graph line is discontinuous due to separate piecewise multilevel model analyses, which used independent variables relative to each time point. MADRS = Montgomery-Åsberg Depression Rating Scale; PHQ-9 = 9-item Patient Health Questionnaire