Depression and cancer risk: a systematic review and meta-analysis.

OBJECTIVE: To assess the associations between depression and incident cancer risk.

STUDY DESIGN: Systematic review and meta-analysis.

METHODS: The Cochrane Library, Web of Science, MEDLINE, and PubMed databases were searched to identify studies. The quality of included studies was assessed using the Newcastle Ottawa Scale. Risk ratios (RRs) were used to measure effect size. A random-effects model was applied to synthesize the associations between depression and cancer risk. A forest plot was produced to visually assess RRs and 95% confidence intervals (CIs). Heterogeneity across studies was assessed using the I-squared statistic. A funnel plot was generated to assess potential publication bias, and Egger's regression was applied to test the symmetry of the funnel plot.

RESULTS: In total, 1,469,179 participants and 89,716 incident cases of cancer from 25 studies were included. Depression was significantly associated with overall cancer risk (RR = 1.15, 95% CI: 1.09-1.22) and with liver cancer (RR = 1.20, 95% CI: 1.01-1.43) and lung cancer (RR = 1.33, 95% CI: 1.04-1.72). Subgroup analysis of studies in North America resulted in a significant summary relative risk (RR = 1.30, 95% CI: 1.15-1.48). No significant associations were found for breast, prostate, or colorectal/colon cancer. The average Newcastle Ottawa score was 7.56 for all included studies.

CONCLUSION: Our findings showed a small and positive association between depression and the overall occurrence risk of cancer, as well as liver cancer and lung cancer risks. However, multinational and larger sample studies are required to further research and support these associations. Moreover, confounding factors such as cigarette smoking and alcohol use/abuse should be considered in future studies.