Association between depressive symptoms and second primary cancer in cancer survivors: Insights from a nationally representative study

Objective: The purpose of this study was to investigate the association between depressive symptoms and second primary cancer (SPC) in U.S. cancer survivors. Methods: Cancer survivors from the 2005-2018 National Health and Nutrition Examination Survey (NHANES) were included in this cross-sectional study, and depressive symptoms were defined by the Patient Health Questionnaire 9 (PHQ-9). The association between depressive symptoms and SPC was assessed via multiple logistic regression, restricted cubic spline (RCS), sensitivity, and subgroup analyses. Results: This study involved 2315 participants representing >15 million noninstitutionalized U.S. residents. Multivariate logistic regression fully adjusted for confounders revealed that cancer survivors with a PHQ-9 score >= 10 had a greater risk of developing SPC than those with a PHQ-9 score of 0-4 ([OR] = 1.88, 95% [CI] = 1.20-2.89, p = 0.005). The RCS showed a linear positive correlation between the PHQ-9 score and SPC (p for overall = 0.017). The robustness of this association was subsequently confirmed via multiple interpolation of missing data and different cluster-level methods (namely weighted linear regression) as sensitivity analyses. Furthermore, subgroup analyses confirmed this correlation was stronger in participants with sleep duration <7 h (p for interaction = 0.036). Conclusion: Moderate to severe depressive symptoms in cancer survivors were associated with an increased risk of developing SPC, especially at <7 h of sleep.