Effect of exercise intensity on depressive symptoms in women

Exercise has been shown to relieve depressive symptoms, yet optimal exercise intensity for treating depression has not been established. The mechanisms that explain the antidepressant effect of exercise also require investigation. The purpose of this study was to test (a) the effect of two different exercise intensities prescribed for aerobic training on depressive symptoms, and (b) a previously proposed psychological mechanism for this effect: self-efficacy. Sedentary women scoring ≥14 on the Beck Depression Inventory-II (BDI-II) were randomized to one of two aerobic training groups that differed on exercise intensity (high [65–75% MaxVO2 reserve] or low [40–55% MaxVO2 reserve]), or to a stretching control group for 10 weeks. Main outcome variables included depressive symptoms (BDI-II) and self-efficacy (exercise self-efficacy [ESE] and depression coping self-efficacy [DCSE]), which were measured at study entry, 5 and 10 weeks later. Participants in all groups (high, n = 18; low, n = 18; stretching, n = 18) had significant reductions in depressive symptoms at Week 5 (p < .001) and Week 10 (p < .001). The BDI-II change scores did not differ significantly among the groups (p = .066). Follow-up analyses controlling for baseline BDI-II scores showed that the high intensity group had significantly fewer depressive symptoms than the low intensity and stretching control groups at weeks 5 and 10 (p < .05). There was no significant association between changes in aerobic capacity and changes in depressive symptoms (r = −.099, p = .491). At 10 weeks, both ESE (p = .013) and DCSE (p < .001) increased significantly for the whole sample, with no significant group difference (p = .613 for ESE, p = .277 for DCSE). Controlling for baseline scores, the increase remained significant for ESE (p = .005) but not for DCSE (p = .629). Partial correlations showed significant negative relationships between both types of self-efficacy and depressive symptoms at Week 5 and Week 10 (p < .02). We concluded that both high and low intensity aerobic exercise, as well as stretching exercise were associated with reductions in mild to moderate depressive symptoms in initially sedentary women. Changes in depression were associated with changes in ESE and DCSE.