Depression and the Risk of Breast Cancer: A Meta-Analysis of Cohort Studies

Background: Whether depression causes increased risk of the development of breast cancer has long beendebated. We conducted an updated meta-analysis of cohort studies to assess the association between depressionand risk of breast cancer. Materials and
Methods: Relevant literature was searched from Medline, Embase,Web of Science (up to April 2014) as well as manual searches of reference lists of selected publications. Cohortstudies on the association between depression and breast cancer were included. Data abstraction and qualityassessment were conducted independently by two authors. Random-effect model was used to compute the pooledrisk estimate. Visual inspection of a funnel plot, Begg rank correlation test and Egger linear regression test wereused to evaluate the publication bias.
Results: We identified eleven cohort studies (182,241 participants, 2,353cases) with a follow-up duration ranging from 5 to 38 years. The pooled adjusted RR was 1.13(95% CI: 0.94 to1.36; I2=67.2%, p=0.001). The association between the risk of breast cancer and depression was consistent acrosssubgroups. Visual inspection of funnel plot and Begg’s and Egger’s tests indicated no evidence of publicationbias. Regarding limitations, a one-time assessment of depression with no measure of duration weakens the test ofhypothesis. In addition, 8 different scales were used for the measurement of depression, potentially adding to themultiple conceptual problems concerned with the definition of depression.
Conclusions: Available epidemiologicalevidence is insufficient to support a positive association between depression and breast cancer.