Six weeks of guided outdoor activity helped a group of military patients with depression and the main result was simpler than the surfing-versus-hiking setup might suggest. Across 96 active duty participants with major depressive disorder, both programs were linked to lower depression scores and the overall improvement path looked much the same in each group.
The trial, published in BMC Psychiatry, compared Surf Therapy and Hike Therapy in people already receiving care through a military wellness program in San Diego. The researchers expected surfing to do better because exercise near water is often discussed as a possible mental-health advantage, yet the central finding stayed more restrained: symptom trajectories did not clearly differ between the two therapies.
Depression remains common far beyond this one trial. The National Institute of Mental Health says an estimated 21.0 million U.S. adults had at least one major depressive episode in 2021. The service-member study matters because it tested whether structured group activity in the natural world could work as an extra layer of care, rather than a replacement for therapy or medication.
How the trial was built
The study drew from active duty personnel referred to the Wounded, Ill and Injured Wellness Program at Naval Medical Center San Diego between January 2018 and March 2020. Researchers screened 110 service members, then enrolled 96 who met diagnostic criteria for depression and randomly assigned 48 to surfing and 48 to hiking.
Each program ran for six weeks. Participants completed clinical interviews and self-report questionnaires before the program, shortly after it ended and again three months later. Session-level mood checks were also taken before and after each weekly activity, which let the team examine both longer-term change and the short lift that might happen during a single outing.
Most of the sample was already receiving other treatment. The paper reports that 90.6% had concurrent depression treatment, 65.6% were using pharmacotherapy and 89.6% were in psychotherapy. Completion rates were respectable for a real-world clinical program: 77.3% met the program’s completion threshold, 91.7% completed at least one follow-up assessment and 78.1% completed both follow-up assessments.
What changed after six weeks
On the clinician-rated MADRS scale, average depression severity fell from 27.45 before treatment to 18.96 after treatment. On the self-reported PHQ-9, the average score moved from 16.67 to 11.78, which means the group shifted from moderately severe symptoms toward the moderate range.
Those are meaningful changes, but the comparison between the two activities stayed narrow. Hike participants tended to report higher average depression scores than surf participants, yet the rate of improvement over time did not significantly differ between groups. In plain terms, one group did not show a distinctly steeper recovery curve than the other.
Weekly sessions also seemed to help in the moment. Using the four-item PHQ-4, the researchers found significant pre-session to post-session improvement in combined depression and anxiety symptoms across both activities. That pattern fits the idea that time outdoors, physical exertion and group participation can all provide immediate relief, even before any longer follow-up is considered.
Several smaller findings help explain why the authors treated the results as clinically encouraging rather than merely statistically positive. Larger clinician-rated improvement was linked to attending more sessions and self-reported PHQ-9 improvement was stronger among participants who were also using pharmacotherapy. The measures themselves were not casual check-ins: the study used blinded clinical assessments, formal diagnostic interviews and reliability checks on a subset of ratings. That makes the paper more persuasive than a simple before-and-after mood survey, even though it still stops short of proving that either outdoor program should replace standard depression treatment.
Why surfing did not clearly beat hiking
The authors began with a plausible reason to expect surfing to win. Work on blue space suggests that water settings may add a distinct sensory and emotional benefit beyond what people get from exercise on land. Surfing also combines movement, attention to changing waves and a novel setting that can feel absorbing.
Even so, hiking shared many of the trial’s most important ingredients. Both programs were social, both took place outdoors and both asked participants to move regularly in a natural environment. Because those broad ingredients overlap so strongly, the trial may have been comparing two active therapies that already carried many of the same useful features.
Baseline differences also complicate any simple winner-take-all reading. Hike participants were somewhat younger on average and started with higher self-reported PHQ-9 scores. The paper’s own discussion argues that water-based effects may be subtle enough to vanish inside the statistical noise when two strong outdoor activities are placed side by side, even if they might show up more clearly against an indoor or wait-list comparison.
What happened at follow-up
The most eye-catching gap arrived later, not during the main symptom-trajectory analysis. At postprogram, the groups did not differ significantly in MDD remission status. By the three-month follow-up, however, 74% of surf participants were no longer classified with MDD, compared with 47% of hike participants.
That number deserves attention, although it also needs caution. The paper notes that the hiking group had more missing data at the three-month follow-up, which may have influenced the remission comparison. The authors also reported that neither therapy showed significant within-group change from postprogram to follow-up, so the remission split should be read as an interesting later difference, not as proof that one therapy produced a clearly stronger symptom trajectory from start to finish.
A later follow-up analysis from the same trial reported that both therapies improved several related psychological and functional outcomes, while surf therapy showed some stronger immediate effects on positive affect and pain. Taken together, the papers suggest that surfing may hold some specific advantages, but the depression comparison in this core trial still does not support a clean verdict that surf therapy broadly outperformed hiking.
What this means for depression care
The most practical message is that both programs looked useful as adjunctive care. The researchers did not test these activities as stand-alone treatment and the paper repeatedly frames them as additions to ordinary clinical care. That matters because almost everyone in the sample was also receiving psychotherapy, medication, or both.
Accessibility also leans in hiking’s favor. Surfing requires equipment, instructors, transportation and access to a coastline. Hiking still needs organization and safe group support, but it can usually be offered in more places and at lower cost. For a clinician or health system deciding what can realistically be delivered, comparable depression trajectories make that practical difference hard to ignore.
The study was also limited to active duty service members, so it cannot automatically predict what will happen in civilians, older adults, or people with different levels of illness. Still, the trial gives a solid answer to a focused question: outdoor activity programs can sit beside standard treatment and help many participants feel better, while the headline comparison between waves and trails remains more balanced than the hook might imply.
Design details support that restrained reading. The trial was preregistered at ClinicalTrials.gov, used blinded assessors for the main clinical ratings and tracked participants across three time points instead of stopping at the end of the six-week program. For readers looking for a simple champion, the more defensible conclusion is narrower: both outdoor therapies helped, surf therapy showed one later remission edge and the overall symptom-improvement trajectories did not clearly separate.
