Social support and physical activity as moderators of life stress in predicting baseline depression and change in depression over time in the Women's Health Initiative.

Purpose: To determine whether social support and/or physical activity buffer the association between stressors and increasing risk of depression symptoms at baseline and at 3-year follow-up.

Methods: This is a secondary analysis of data from the Women's Health Initiative Observational Study. 91,912 community-dwelling post-menopausal women participated in this prospective cohort study. Depression symptoms were measured at baseline and 3 years later; social support, physical activity, and stressors were measured at baseline.

Results: Stressors at baseline, including verbal abuse, physical abuse, caregiving, social strain, negative life events, financial stress, low income, acute pain, and a greater number of chronic medical conditions, were all associated with higher levels of depression symptoms at baseline and new onset elevated symptoms at 3-year follow-up. Social support and physical activity were associated with lower levels of depressive symptoms. Contrary to expectation, more social support at baseline strengthened the association between concurrent depression and physical abuse, social strain, caregiving, and low income. Similarly, more social support at baseline increased the association between financial stress, income, and pain on new onset depression 3 years later. Physical activity similarly moderated the effect of caregiving, income, and pain on depression symptoms at baseline.

Conclusion: Stressors, social support, and physical activity showed predicted main effect associations with depression. Multiplicative interactions were small in magnitude and in the opposite direction of what was expected.