Brown, J.C., Huedo-Medina, T.B., Pescatello, L.S., Ryan, S.M., Pescatello, S.M., Moker, E., . . . Johnson, B.T. (2012). The efficacy of exercise in reducing depressive symptoms among cancer survivors: A meta-analysis. PloS One, 7(1), e30955.

To perform a meta-analysis and systematic review to determine the efficacy of exercise in reducing the symptoms of depression among cancer survivors

• Databases searched were PubMed, PsycINFO, CINAHL Plus, SPORTDiscus, and ProQuest medical databases. In addition, investigators searched reference lists for relevant studies.
• Search keywords were cancer (and related terms), depression OR anxiety (and similar terms) AND exercise (and associated terms).
• Included studies were RCTs involving exercise, adults who had survived some form of cancer, and at least one measure of depression.
• Authors excluded studies involving children.

• The sample was composed of 14,702 participants.
• Except for noting the general method of collecting data, authors did not report the evaluation method.

• The number of studies included in the sample was 37; the number of participants was 2,929. Authors did not provide the sample range across studies.
• The sample included patients with breast, prostate, and colorectal cancers as well as patients with leukemia and lymphoma.

Late effects and survivorship

• The intensity of exercise was low to moderate, according to calculations of metabolic equivalent of task (MET).
• Exercise interventions most often occurred during curative treatment. 
• Compared to standard care, exercise provided a small reduction in measures of depression symptoms. Subgroup analysis showed this effect among breast cancer patients only (d = –0.19, 95% CI –0.28, –0.09). Moderators of the effect were increases in the amount of aerobic exercise per week: Aerobic exercise reduced depression in dose-response fashion. 
• Effects were greatest when exercise sessions were supervised.

Findings support the conclusion that exercise has a small positive effect on symptoms of depression among women with breast cancer.

• Studies were highly heterogeneous, even just those studies of patients with breast cancer.
• Authors state that included studies were limited by sample size and quality issues, but they do not describe how they assessed study quality.
• In most studies, depression symptoms were at a very low level at baseline.
• Effect sizes were very small.

Findings suggest that supervised aerobic exercise may be helpful in reducing mild symptoms of depression among women with breast cancer. Applicability of the findings to patients with other diagnoses is unclear.