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Objectives: Physical activity has been found to alleviate depression, but little is known about the mechanisms of change. This study assessed whether depression and hypothesised mechanisms - self-esteem, physical self-perceptions, self-efficacy, positive affect (PA) and negative affect (NA) - changed over time among depressed individuals who increased their physical activity. It also assessed the temporal relation of change. Design: Longitudinal, within-subjects design. Method: Thirty-nine individuals with elevated symptoms of depression increased their physical activity for an eight-week period. Measures of depression and the hypothesised mechanisms were taken at baseline, week one, week three and week eight. Results: There were statistically significant improvements in depression and all the potential mechanisms between baseline and week eight. An initial reduction in depression was observed at week one, with most of the reduction occurring by week three. Initial improvement in PA, NA and self-efficacy also occurred at week one, while initial improvement in self-esteem and self-perceptions occurred at week three. Further improvement in self-esteem and some of the self-perception variables was observed after there was no further significant change in depression. There were larger changes in PA than the other measured mechanisms at weeks one and three. Conclusions: Change in PA, NA and self-efficacy present stronger candidate mechanisms than change in self-esteem and self-perceptions for mediating change in depression, at least in the early stages of increased activity. An increase in PA may be especially important. However, a causal role for the potential mechanisms cannot be determined from this study. © 2009 Elsevier Ltd. All rights reserved.

Original publication




Journal article


Mental Health and Physical Activity

Publication Date





44 - 52