Depression, antidepressant use, and breast cancer incidence in the Sister Study cohort

Depression could affect breast cancer risk; however, epidemiologic findings are mixed. We assessed the association of breast cancer risk with self-reported history of diagnosed depression and time-dependent antidepressant use.

We analyzed data from 45,746 women in the Sister Study cohort (2003-2009). Cox proportional hazard regression was used to estimate hazard ratios (HR) for breast cancer.

During follow-up (mean = 11.7 years), 3,899 breast cancers were diagnosed. There was no association between history of diagnosed depression and risk of breast cancer (HR = 0.98, 95%CI = 0.91-1.06). However, antidepressant use was associated with reduced risk of breast cancer (HR = 0.92, 95%CI = 0.85-1.00). Comparison of antidepressant drug classes revealed a suggestion of an inverse association with selective serotonin reuptake inhibitors (SSRIs, HR = 0.90, 95%CI = 0.81-1.00). Reduction was stronger in those with BMI < 25 (HR = 0.72, 95%CI = 0.59-0.89).

Depression was not associated with breast cancer risk. We observed a suggestion of a reduction in risk associated with antidepressant use. The analysis evaluating the association by specific drug types, showed a suggestion of a reduction in breast cancer risk associated with use of SSRIs. The negative association with overall antidepressant use and SSRIs, was stronger in those with BMI < 25, which could reflect a dose effect. This was the first study to examine the association between depression, antidepressant use, and breast cancer risk in a large genetic-risk-enriched cohort.