Interleukin-6 and depressive symptom severity in response to physical exercise.

Elevated IL-6 has been implicated in depression. The anti-inflammatory effects of exercise may be associated with its clinical efficacy for depression. We determined if serum IL-6 levels were altered by 12 weeks of physical exercise, and if IL-6 levels were associated with baseline depression severity and change in depression severity in response to exercise. Data from 116 adults (42.7±11.5y) with mild-to-moderate depression (Patient Health Questionnaire >9) who participated in the physical exercise arm of the Regassa RCT (www.regassa.se) were analyzed. Participants were requested to complete three 60-min exercise sessions weekly for 12 weeks. Blood samples were provided at baseline and post-intervention following an overnight fast and were analyzed for serum levels of IL-6 using ELISA. IL-6 values were logarithm-transformed. Higher baseline serum IL-6 levels were significantly associated with reduced depression severity after exercise. Reduced IL-6 levels following exercise were significantly associated with parallel reductions in depression severity. These findings are consistent with a previously reported association between reduced serum IL-1β levels and reduced depression severity following 12 weeks of physical exercise in 105 depressed adults. Findings support associations between IL-6, depressive symptoms, and exercise response, and provide support for the plausible involvement of IL-6 in the antidepressive effect of exercise.