Physical activity dose-response effects on outcomes of depression and anxiety

Purpose: The purpose of this study was to examine the scientific evidence f or a dose-response relation of physical activity with depressive and anxiet y disorders. Methods: Computer database searches of MEDLINE, PsychLit, and Internet and personal retrieval systems to locate population studies, rando mized controlled trials (RCTs), observational studies, and consensus panel judgments were conducted. Results: Observational studies demonstrate that g reater amounts of occupational and leisure time physical activity are gener ally associated with reduced symptoms of depression. Quasi-experimental stu dies show that light-, moderate-, and vigorous-intensify exercise can reduc e symptoms of depression. However, no RCTs have varied frequency or duratio n of exercise and controlled for total energy expenditure in studies of dep ression or anxiety. Quasi-experimental and RCTs demonstrate that both resis tance training and aerobic exercise can reduce symptoms of depression. Fina lly, the relation of exercise dose to changes in cardiorespiratory fitness is equivocal with some studies showing Chat fitness is associated with redu ction of symptoms and others that have demonstrated reduction in symptoms w ithout increases in fitness. Conclusion: All evidence for dose-response eff ects of physical activity and exercise come from B and C levels of evidence . There is little evidence for dose-response effects, though this is largel y because of a lack of studies rather than a lack of evidence. A dose-respo nse relation does, however, remain plausible.