Exercise may help ease symptoms of depression, according to a fresh look at past research.
Researchers who analyzed data from previous studies found people who exercised experienced a "moderate" reduction in their depressive symptoms compared to those who did other activities, such as using relaxation techniques, or received no treatment.
"This review provides some additional evidence that there may be some benefit (to exercise)," Dr. Gillian Mead, the study's senior author from the University of Edinburgh in Scotland, told Reuters Health.
A 2009 review from the Cochrane Collaboration, an international organization that evaluates medical research, found similar results, but more studies looking at the link between exercise and depression have since been published.
"We'd become aware of some new trials in the area and - in general - the Cochrane review should be kept updated if there is new evidence that may lead to changes," Mead said.
About one in ten Americans reports being depressed, according to the U.S. Centers for Disease Control and Prevention. The most popular treatments for depression include antidepressant medications and psychotherapy.
Mead and her fellow researchers write in The Cochrane Library, however, that many people prefer alternative treatments, and some doctors recommend exercise as a potential option.
For the new review, they searched databases for all medical trials conducted through March 2013 that compared exercise among adults with depression to other activities or no treatment.
Overall, the researchers were able to combine data from 35 trials that included 711 people who were randomly assigned to an exercise program and 642 who were randomized to comparison groups.
Because the studies used various scales to assess depression, they converted the results into a single measurement to compare people in exercise and non-exercise groups. Using that measurement, a difference between groups of 0.2 represents a small effect, 0.5 a moderate effect and 0.8 a large effect.
Mead's team found a 0.62-point difference in depressive symptoms favoring people who exercised.
In one of the included trials from 2007, for instance, researchers found 45 percent of people who took part in supervised exercise no longer met the criteria for depression after four months, compared to 31 percent taking an inert placebo