“The increased risk is definitely there, but we’re not entirely sure why,” said the study leader, Dr Gail Daumit from the Johns Hopkins University School of Medicine (United States) in a news release.
The findings raise questions about whether people with serious mental illness receive appropriate cancer screenings and preventive care to help them avoid cancer risk factors such as smoking.
For the study, researchers analysed data from more than 3 300 patients with schizophrenia and bipolar disorder to determine how many of them were diagnosed with cancer between 1994 and 2004.
Compared to the general population, schizophrenia and bipolar patients were almost five times more (4,5 times) more likely to develop lung cancer, 3,5 times more likely to develop colorectal cancer, and nearly three times more likely to develop breast cancer, the researchers found.
According to Daumit, people with serious mental illness often smoke, which could explain their elevated risk for lung cancer. She also noted that women with schizophrenia and bipolar disorder are less likely to have children and that childbearing is believed to reduce breast cancer risk. In addition, some drugs used to treat mental illness can increase levels of the hormone prolactin, a factor that has been linked to breast cancer.
The increased risk of colorectal cancer could be due to lifestyle issues such as smoking, lack of exercise and a diet lacking fruits and vegetables, Daumit said.
While the study uncovered a link between mental illness and cancer risk, it did not prove that one causes the other.
Source: HealthDay News