Objective: The objective was to characterize the relationship between depression and incident cancer. Few studies have employed population-based prospective data on subtypes of cancer to address the question.
Method: A population-based sample of 3,177 cancer-free adults from the Baltimore Epidemiologic Catchment Area Study who have been followed for 24 years. Cox proportional hazards models were used to estimate relative hazards for both overall and subtype-specific cancers among those with a history of depression.
Results: The risk set contained 334 incident cancer cases and 40,530 person-years of observation. DIS/DSM-III major depression was associated with a higher hazard for overall cancer (HR: 1.9, 95% CI: 1.2, 3.0) and a statistically significant increased hazard for breast cancer (HR: 4.4, 95% CI: 1.08, 17.6) among women. There was a positive association between history of depression and prostate cancer, but confidence bounds included the null. No reliable associations were found between colon, lung, or skin cancers and depression. The pattern of results was similar for dysphoria, but not for phobia or any other mental disorder studied.
Conclusions: Results reveal a specificity to the association between depression and hormonally mediated cancers, which provides support to hypotheses about a common biological pathway between depression and cancer. Further research can build on observational studies to examine the mechanisms through which our emotions affect our health.