Leisure-time physical activity and perceived stress mediated the impact of social support on depressive symptoms among breast cancer survivors


Objective: Models of interpersonal behaviours suggest that social support may foster both the reduction in stress and the adoption of health protective behaviours [e.g., leisure-time physical activity (LTPA)], which may improve mental health. Therefore, this study assesses whether change in both perceived stress and LTPA mediate the association between change in social support and change in depression symptoms among breast cancer survivors (BCS). Methods: Adult BCS (N = 199) volunteered for the study. Approximately six months following the completion of systemic treatments, social support, LTPA, perceived stress, pain symptoms, and depressive symptoms were self-reported at the beginning (baseline) and the end (follow-up) of a 6-month period using reliable and valid questionnaires. Given that pain symptoms tend to co-occur with depressive symptoms in BCS, they were controlled in the analysis along with age, education, body mass index, stage of breast cancer and time since diagnosis. Multiple regression analyses were performed using residual change scores. Bias –corrected and –accelerated bootstrap estimates (5000 bootstrap samples) with 95% confidence intervals (BCa 95%CI) were obtained for the mediated effects. Multiple imputation was used to account for lost to follow-up (25%). Results: An increase in social support leaded to a decrease in depressive symptoms. This effect was mediated by change in both LTPA (indirect effect = -0.03 [-0.06, -0.001]) and perceived stress (indirect effect = -0.07 [-0.09, -0.05]). Moreover, the percentage of explained variance in the main model [F(9,189) = 13.02; p < 0.0001] was 38%, and results from multiple imputation and complete cases analysis were similar. Conclusions: Participation in LTPA and reduction in perceived stress are two pathways through which social support contributes to lower depressive symptoms in BCS. Therefore, social support represents a valuable intervention target for improving mental health in the aftermath of breast cancer. 

Acknowledgments: This study is funded by a CIHR operating grant awarded to Dr. Catherine M. Sabiston (PI) and Dr. Carsten Wrosch (CO-I)