Selective serotonin reuptake inhibitors (SSRIs) and breast cancer : a record linkage study
Ashbury, Janet E.
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Evidence suggests that selective serotonin reuptake inhibitors (SSRIs, a class of antidepressant medications) may contribute to increased breast cancer risk by stimulating the secretion of prolactin, a potential tumour promoter. The main objective of this study was to determine breast cancer risk associated with the duration, dosage and timing of SSRI use among women, with control for a limited set of confounders. This thesis project, conducted within the context of a population-based two-stage case-control study, consisted of a record linkage study utilizing three Saskatchewan health services databases. Cases included 1,273 women with primary breast cancer diagnosed between January 1, 2003 and December 31, 2005, and controls consisted of 12,730 subjects randomly selected from the province’s population registry. Data on SSRI use was compiled from the Saskatchewan prescription drug plan database. Information on a limited set of established risk factors for breast cancer that may confound this relationship was ascertained from the population registry and the prescription database. Cases and controls were similar in terms of age, total number of consecutive years eligible for prescription coverage and indicators of socioeconomic status. Compared to controls, cases were more likely to be married and to have used hormone therapy and/or oral contraceptives. Compared to nonusers, results indicated that the use of SSRIs for three or more years (as estimated by having filled 36 or more prescriptions for all SSRIs combined during the main exposure window more than two years prior to index date) was not associated with an increased risk of breast cancer (OR= 1.08, 95% CI: 0.74-1.58), controlling for age, marital status, oral contraceptive and hormone therapy use. In addition, no suggestion of increased risk was detected for long-term exposures to individual SSRIs (24 or more prescriptions filled during the main exposure window) and in relation to total combined SSRI use 2-7 years and more than seven years prior to index date. However, these risk estimates may have been affected by potential sources of information bias and confounding. In summary, these results do not provide evidence to suggest that the risk of breast cancer is increased with the use of SSRIs.