Aerobic Exercise or Stretching As Add-on to Inpatient Treatment of Depression: Similar Antidepressant Effects on Depressive Symptoms and Larger Effects on Working Memory for Aerobic Exercise Alone.

Background: Aerobic exercise (AE) has positive effects on symptom severity and cognitive symptoms of depression. Since data on AE as add-on to inpatient treatment in depression is still scarce, we conducted this double-blind randomized controlled study. Methods: Patients aged between 18 and 60 years were recruited into the study if Hamilton Depression Rating Scale 17 (HDRS-17) score was >16. Participants were randomly assigned to either AE or basic stretching activities (control), which took place 3x/week for 6 weeks. Primary outcome was depression severity as assessed with the HDRS-17 and the Beck Depression Inventory (BDI). Further physiological and psychological variables and cognitive performance were assessed as secondary outcomes. Results: Forty-two patients were included in the analysis (exercise: n = 22; control: n = 20). Regardless of group allocation, we found a significant short-term time effect for symptom-severity (HDRS17: p<0.001, eta(2)=0.70; BDI: p<0.001, eta(2)=0.51), mental toughness (p<0.001, eta(2)=0.32), physical self-description endurance score (p = 0.013, eta(2)=0.16), cognitive flexibility (p = 0.013, eta(2)=0.14), and body mass index (BMI) (p = 0.006, eta(2)=0.19). Working memory showed a significant time by group interaction in favor of AE (p= 0.043, eta(2)=0.10). Short-term effects on symptom severity, mental toughness and BMI remained stable across the 6-month followup period. Finally, self-reported physical activity increased significantly from baseline to follow-up (p = 0.014, eta(2)=0.15). Limitations: The sample-size is rather small. The control intervention might have been too active as to find a time by group interaction for symptom severity. Conclusions: AE was associated with comparably large depression alleviation vs. stretching and with add-on benefits on working memory.