Background: Physical inactivity and comorbid depressive
symptoms are prevalent among patients with a
chronic illness. To our knowledge, randomized controlled
trials of the effects of exercise training on depressive
symptoms among patients with a chronic illness have
not been systematically reviewed.We estimated the population
effect of exercise training on depressive symptoms
and determined whether the effect varied according
to patient characteristics and modifiable features of
exercise exposure and clinical settings.
Methods: Articles published before June 1, 2011, were
located using the Physical Activity Guidelines for Americans
Scientific Database, Google Scholar, MEDLINE,
PsycINFO, PubMed, and Web of Science. Ninety articles
involving 10 534 sedentary patients with a chronic illness
were selected. Included articles required (1) randomized
allocation to an exercise intervention or nonexercise
comparison condition and (2) a depression outcome assessed
at baseline and at mid- and/or postintervention.
Hedges d effect sizes were computed, study quality was
evaluated, and random effects models were used to estimate
sampling error and population variance of the observed
effects.
Results: Exercise training significantly reduced depressive
symptoms by a heterogeneous mean effect size delta
() of 0.30 (95% CI, 0.25-0.36). Larger antidepressant
effects were obtained when (1) baseline depressive symptoms
were higher, (2) patients met recommended physical
activity levels, and (3) the trial primary outcome, predominantly
function related, was significantly improved
among patients having baseline depressive symptoms indicative
of mild-to-moderate depression.
Conclusions: Exercise reduces depressive symptoms
among patients with a chronic illness. Patients with depressive
symptoms indicative of mild-to-moderate depression
and for whom exercise training improves functionrelated
outcomes achieve the largest antidepressant effects.