Exercise and clinical depression: examining two psychological mechanisms

Objectives: To examine the antidepressant effects of exercise, and two previously proposed psychological mechanisms for this effect: self-efficacy and distraction. Method: A quasi-experimental design was utilized with participants (N = 19) self-selecting to either a control or a 9-week exercise group. Dependent variables included severity of depression, coping self-efficacy, rumination, and distraction and were measured at study entry, 3 and 9 weeks later. Results: Exercisers reported lower depression scores than controls at Week 3 [9.3 (4.8) vs. 24.7 (12.0), p < 0.05] and Week 9 [6.4 (5.4) vs. 21.8 (16.4), p < 0.05]. Coping self-efficacy was higher among exercisers than controls at Week 3 [7.3 (0.9) vs. 5.2 (1.3), p < 0.05] and Week 9 [7.5 (0.9) vs. 5.3 (1.8), p < 0.05]. Exercisers ruminated less than controls at Week 3 [38.9 (1.8) vs. 46.5 (8.2), p < 0.05] and at Week 9 [33.9 (1.2) vs. 44.0 (10.9), p < 0.05]. Distraction was higher for exercisers at Week 3 [28.6 (1.2) vs. 23.6 (3.0), p < 0.05] but not at Week 9 [27.7 (2.1) vs. 23.7 (5.3), p > 0.05]. Partial correlations, controlling for baseline values of the independent variables, were conducted and a significant negative relationship between coping self-efficacy and depression was found at both Weeks 3 and 9. Conclusions: Exercise was associated with a reduction in the symptoms of depression. Support was found for coping self-efficacy as a potential mechanism; however, there was limited support for distraction as a potential mechanism. (C) 2003 Elsevier Ltd. All rights reserved.