Use of certain anti-psychotic medications may up a woman's risk of breast cancer, according to Harvard researchers.

Animal studies have raised the possibility that prolactin-elevating dopamine antagonists (anti-psychotic medications that affect a pituitary hormone that stimulates and maintains the secretion of milk) used to treat psychotic disorders may cause and promote breast cancer. However, studies in humans have been limited and inconsistent.

Researchers conducted a study of 52,819 women exposed and 55,289 not exposed to dopamine antagonists between January 1, 1989 and June 30, 1995. All of the women were 20 years old or older and initially free of breast cancer. Cases of breast cancer were identified through a cancer registry and incidences of breast cancer surgeries.

Use of anti-psychotic dopamine antagonists was linked with a 16 percent increase in the risk of breast cancer, according to their report published in the Archives of General Psychiatry. The increased risk was also seen in women who used prolactin-elevating anti-emetic (anti-nausea) dopamine antagonists despite having different breast cancer risk profiles than users of anti-psychotic dopamine antagonists.

"Anti-psychotic dopamine antagonist use may confer a small but significant risk of breast cancer," concluded the researchers. In light of the small hazards, these findings should lead to follow-up investigations but not to changes in treatment strategies, they added.

Other sources: Archives of General Psychiatry