Background: Animal and human studies have reported an association between antidepressant (AD) medication use and breast cancer risk. A population-based case-control study was designed specifically to examine this association among women in Ontario, Canada.
Methods: The Ontario Cancer Registry (OCR) identified women diagnosed with primary breast cancer. Controls, randomly sampled from the female population of Ontario, were frequency matched by 5-year age groups. A mailed self-administered questionnaire included questions about lifetime use of AD and potential confounders. Multivariate logistic regression yielded odds ratio estimates.
Results: 'Ever' use of AD was reported by 14% (441/3077) cases versus 12% (372/2994) controls. The age-adjusted odds ratio (AOR) for 'ever' use was 1.17, (95% CI: 1.01, 1.36). An increased risk was also observed for selective serotonin reuptake inhibitors = 1.33 (95% CI: 1.07, 1.66), Sertraline = 1.58 (95% CI: 1.03, 2.41), and Paroxetine = 1.55 (95% CI: 1.00, 2.40). None of the 30 variables assessed for confounding altered the risk estimate by more than 10%. Multivariate adjustment including all possible breast cancer risk factors yielded an unchanged, but not significant, point estimate (MVOR = 1.2, 95% CI: 0.96, 1.51). No relationship was observed for duration or timing of AD use.
Conclusions: A modest association between 'ever' use of AD and breast cancer was found using the most parsimonious multivariate model. OR estimates did not change, but CI were widened and statistical significance lost, after adjustment for factors associated with breast cancer risk.