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Depression has been associated with higher levels of proinflammatory cytokines such as interleukin (IL) 6 and tumor necrosis factor α (TNF; e.g., NEJM JW Psychiatry Mar 29 2010). In addition, selective serotonin reuptake inhibitors (SSRIs) lower cytokines, such as Il-1β, and elevated TNF levels seem to predict resistance to SSRI treatment. In the current randomized study, 73 depressed patients with inadequate SSRI response started a 12-week, adjunctive exercise program at low or high intensity. Cytokine levels were examined at baseline and posttreatment.
Higher levels of TNF at baseline predicted better depression scores at week 12. Degree of depression improvement was associated with change in Il-1β, but this association was significant only in the high-exercise group. Exercise did not significantly change overall levels of the tested cytokines (TNF, Il-1β, Il-6, and interferon-γ).
Rethorst CD et al. Pro-inflammatory cytokines as predictors of antidepressant effects of exercise in major depressive disorder. Mol Psychiatry 2013 Oct; 18:1119 (http://dx.doi.org/10.1038/mp.2012.125)
Comment
Previous studies have suggested the existence of an “inflammatory” type of depression (NEJM JW Psychiatry Oct 15 2012). If this does exist, the current results suggest that exercise works differently from antidepressants — because higher cytokine levels predict response to exercise but not response to antidepressant medication. Given the growing research data supporting an antidepressant effect of exercise, this biological finding gives heft to suggestions that it be considered in nonresponsive patients who are able to undertake such a program.