TORONTO, CANADA. There is some evidence from animal experiments that antidepressants may promote breast cancer tumors. One case- control study found an association between the use of tricyclic antidepressants and breast cancer risk, but the data concerning SSRIs (selective serotonin reuptake inhibitors) is inconsistent. Researchers at the University of Toronto now confirm that long- term use of tricylic antidepressants is indeed associated with an increased incidence of breast cancer. The study involved 700 women with breast cancer (aged 25 to 74 years) and 700 age-matched controls. A comparison of the use of antidepressants between the cases and the controls found no significant overall differences in breast cancer risks. However, when evaluating the data in detail the researchers discovered that women who had used tricyclic antidepressants for 25 months or more had twice the risk of developing breast cancer as had women who had not used these antidepressants. They also noted that women who had used the SSRI antidepressant paroxetine (Paxil) for more than two weeks had a seven times greater risk of breast cancer even when other possible risk factors were fully accounted for. The researchers caution that the number of women using paroxetine was quite small and recommend larger trials to confirm their initial finding. They do point out though that paroxetine stimulates prolactin secretion and is a potent inhibitor of the cytochrome P450 2D6 enzyme, both factors in an increased breast cancer risk.
Cotterchio, Michelle, et al. Antidepressant medication use and breast cancer risk. American Journal of Epidemiology, Vol. 151, May 15, 2000, pp. 951-57