Physical activity and specific symptoms of depression: A pooled analysis of six cohort studies.

Background: The association between physical activity (PA) and depression is well-established, but the details that explain this association remain elusive. We examined whether PA is differentially associated with specific symptoms of depression (e.g., cognitive vs somatic symptoms), and whether these associations follow a dose-response pattern with respect to intensity or frequency of PA.

Methods: Cross-sectional analyses were based on 6 samples of the continuous U.S. National Health and Nutrition Examination Surveys (NHANES) carried out between 2007 and 2018 (n = 28,520). Depressive symptoms were assessed with Patient Health Questionnaire 9 (PHQ-9). Information about PA (vigorous, moderate, and daily commuting by foot or bike) and covariates was self-reported.

Results: After adjusting for education, health behaviors, body-mass index, physical functioning, and all the other depressive symptoms, lower PA was specifically associated with four depressive symptoms: loss of interest/pleasure, feeling down/hopeless, fatigue, and changes in appetite (odds ratios from 0.94 to 0.59). A monotonic dose-response pattern on PA amount was observed only for interest/pleasure and fatigue, and these associations were independent of PA intensity.

Limitations: Cross-sectional data did not allow us to assess temporal ordering. Both depressive symptoms and PA were self-reported, which may induce bias.

Conclusion: Low PA may be linked to depressive symptoms particularly through the symptoms of anhedonia and fatigue. Given that their association with PA amount follows a dose-response pattern and is independent of PA intensity, we hypothesize that behavioral activation and exposure to rewarding experiences might help to explain why PA alleviates depression.