MedWire News: Women with schizophrenia and those with other serious mental illnesses have a lower risk of developing breast cancer than women in the general population, researchers have found.

"Compared with the general population, schizophrenia patients have been reported to have lower or similar rates of breast cancer despite several risk factors such as excess smoking, obesity and hyperprolactinaemia [excess production of the hormone prolactin]," explain Dr Yoram Barak, from Abarbanel Mental Health Center in Bat-Yam, Israel, and team.

"However, it has been argued that psychiatric [illness] itself may be the confounding factor that affects cancer incidence and not particularly schizophrenia," they add.

To investigate, the researchers studied data the incidence of breast cancer among 2011 female in-patients with schizophrenia and 6243 with other serious mental illnesses, and compared the findings with data on breast cancer incidence in the general population.

The team found that 2.5% of the women with schizophrenia and 1.3% of those with other serious mental illnesses had developed breast cancer at some point in their lives.

Further analysis revealed that, compared with women in the general population, women with schizophrenia were 37% less likely to develop breast cancer and those with other serious mental health illnesses were 46% less likely to develop the condition.

"The major finding of the present study is the reduction in occurrence of breast cancer in both female schizophrenia patients and other serious mental illness patients," Dr Barak and colleagues write in the journal Schizophrenia Research.

"Whether lifestyle, exposure to psychotropics [mental health medications] or characteristics of the psychiatric system drive the mechanism responsible for reduced cancer rates these need be further elucidated."

However, they add that the findings should not reduce the importance of breast screening among female in-patients with serious mental health disorders.