Physical inactivity and co-morbid depressive symptoms are common among patients with a chronic illness, according to Matthew Herring, Ph.D., lead author and research associate in the UAB School of Public Health’s Department of Epidemiology. Herring says it is known that exercise can decrease depressive symptoms, but randomized controlled trials of the effects among patients with a chronic illness had not been systematically reviewed.
The researchers reviewed 90 previous studies of more than 10,500 sedentary patients with a chronic illness who were randomly assigned to exercise training or a non-exercise comparison; trials had to measure depression before and after exercise training. Herring says the results provide evidence to recommend exercise training to patients as a potential low-risk, adjuvant treatment for depressive symptoms that may develop during the course of chronic illness.
“Adverse health outcomes associated with co-morbid depressive symptoms, and not just a co-morbid depressive disorder, are well established and include reduced adherence to prescribed treatments and quality of life, increased disability, symptom burden and use of health-care services,” Herring says.
“Also, because some evidence has questioned the efficacy of pharmacotherapy among patients with co-morbid chronic illnesses, there continues to be interest in alternative therapies including exercise,” Herring says.
Among patients with a chronic illness, exercise training — including aerobic exercise like jogging, cycling and resistance exercise — reduced depressive symptoms by 22 percent overall, researchers reported. Larger improvement was seen in participants who met physical activity recommendations of at least 150 minutes of moderate intensity exercise per week or at least 75 minutes of vigorous intensity exercise. The largest improvements were noted among patients with symptom scores indicative of mild-to-moderate depression and for whom exercise improved function-related outcomes.
“This suggests that it is plausible that exercise-induced depressive symptom reductions are explained in part by improvements in function among patients,” says Herring.
Herring adds that their results have a number of implications for future research. This includes the need for well-designed trials of exercise effects on depressive symptoms among patients with a chronic illness who have had a depressive disorder diagnosed, trials that examine the relation of improved depressive symptoms and improved function among patients and trials that examine the minimal or optimal effective dose of exercise necessary to elicit depressive symptom reductions.