Does Depression Symptom Improvement Following Surf Or Hike Therapy Persist When Controlling For Physical Activity?

Surf and hike therapies have been shown to significantly reduce depression severity. In addition to probable factors such as the natural environment, socialization, or skill mastery, exercise itself may contribute to the improvements reported during surf and hike therapies; however, no study has examined the effects of such interventions when controlling for physical activity. PURPOSE: To identify potential mechanisms of symptom improvement, this study analyzed whether the effects of surf and hike therapies on depression severity remained after controlling for physical activity. METHODS: Participants were 96 active duty service members with major depressive disorder. Total physical activity was recorded using Fitbit Charge 2 accelerometer devices throughout the 6-week program cycles, and quantified into average MET minutes per week. Study outcomes were clinician-assessed (MADRS) and self-report (PHQ-9) depression severity scores from pre- to postprogram, analyzed using multilevel modeling. RESULTS: Sixty-eight percent of the total sample met the US Physical Activity Guidelines (≥450 MET mins/week; M = 374 MET mins/week; SD = 277). Surf and hike therapies significantly reduced depression symptom severity from pre- to postprogram (ps < .001). After controlling for overall physical activity, improvements persisted for both self-reported (PHQ-9 p < .001; MD = -4.92) and clinician-assessed (MADRS p < .001; MD = -7.19) depression severity. CONCLUSIONS: Study results suggest that factors beyond physical activity may be responsible for depression improvements following surf and hike therapies. Future work should examine other influences and contexts of exercise (e.g., environmental, social) to elucidate reasons for symptom change and maximize benefit for depression. Supported by: U.S. Navy Bureau of Medicine and Surgery