Is there a link between antidepressants and breast and ovarian cancer? A new meta-analysis of 61 trials identified a connection in nearly 33 percent of the epidemiological and pre-clinical studies conducted between 1965 and 2010 found an association between cancer and antidepressants. And the link was stronger among women using selective serotonin reuptake inhibitors, or SSRIs.
Moreover, the study found researchers with industry ties were significantly less likely than researchers without those affiliations to conclude antidepressants increase the risk of breast or ovarian cancer. The authors of the meta-analysis, which was published this week in PLoS Medicine, suggest the findings raise public health and policy issues, "because there is increasing evidence that financial ties among industry, investigators, and academic institutions can affect the research process."
Why? It is worth recalling antidepressants are used by some 27 million Americans, and are the third most-prescribed type of med after cholesterol pills and painkillers. SSRIs include Pfizer's Zoloft and GlaxoSmithKline's Paxil. “Reviewing the evidence is a critical public health issue in light of the increasing prevalence of antidepressant use, especially among women, and in light of the fact that one in eight women will be diagnosed with cancer of the breast during their lifetime,” the PLoS authors write.
The researchers detected an 11 percent greater likelihood of women who take an antidepressant of developing either breast or ovarian cancer later in life. But the odds rose when 15 studies funded by drugmakers were yanked from the analsysis. Why? None of those studies found any such link. For instance, none of the four epidemiological studies for which the principal investigator had industry ties reported a positive association between antidepressants and cancer risk. Of the 22 studies for which the PI had no industry ties, 45 precent reported positive findings.
Similarly, none of the 11 pre-clinical studies for which the PI had industry ties reported positive cancer findings, the researchers wrote. Of the 24 studies for which the PI had no industry ties, 42 precent reported antidepressants were carcinogenic or promoted tumors. In total, none of the 15 researchers with industry ties reported positive cancer findings, versus 43 percent of those without industry ties.
Consequently, the researchers posit that "rather than having fewer and less severe side effects, short-term use and/or low dose antidepressants could increase the risk of breast and ovarian cancer in women or exacerbate cancer cell growth in women in the early stages of breast and ovarian cancer." But they also suggest that large-scale prospective cohort studies of women using SSRIs are needed to determine if antidepressants cause or enhance breast and ovarian tumor growth.
The lead author, by the way, has previously explored research involving industry ties. Last year, Lisa Cosgrove, an ethics fellow at Harvard University, explored the links between psychiatrists and drugmakers (back story).
Despite the implications, they conclude by noting the PLoS authors do not wish to suggest that researchers with industry ties "intentionally designed studies to produce results favorable" to drugmakers or misrepresented results. The existence of industry ties "points to a generic risk that a financial conflict of interest may compromise the research process or undermine public trust. Conflicts of interest do not imply that any (specific researcher) is improperly motivated."