A troubling correlation was found for Johns Hopkins University researchers recently, who found that people with serious mental illnesses – schizophrenia, bipolar disorder, and crippling depression – were found more likely to develop cancer and have severe injuries than the general population.

Study leader Gail L. Daumit, MD, MPH, associate professor of medicine and psychiatry at the Johns Hopkins University School of Medicine, and her team analyzed data from 3,317 Maryland Medicaid residents who suffered from schizophrenia and bipolar disorder, and determined whether subjects had gotten cancer in the time period between 1994 and 2004. When compared to the general population, subjects with mental illness were 4.5 times more likely to have lung cancer, 3.5 times more likely to receive colorectal cancer, and three times more likely to have breast cancer.

Why is this happening? Though this particular group is at increased risk for suicide and homicide, Daumit has ruled that out as a risk, since the major killers of the group were cancer and cardiovascular health-related issues – the same as the general population. Daumit has also ruled out any racial or age-related illnesses; there were no racial differences in who developed cancer within the group, and the average subject was 42 to 43 years old.

Daumit and her team have come to several conclusions as to what might be providing this correlation. Those with significant mental illnesses tend more likely to be smokers, and smoking can increase the risk of lung cancer and of colorectal cancer. In addition, this same group is less likely to have children; it is believed that pregnancy and childbirth lowers the risk of breast cancer in women. The team also suggests that colorectal cancer risks may be influenced by lack of physical ability and unbalanced diets.

Previously, Daumit had also published a study that found that people with mental illness were more likely to suffer from severe and fatal injuries. From the study published in Injury Prevention, the research team says, “Injury incidence was 80% higher and risk for fatal injury was more than four and a half times higher among the cohort with serious mental illness compared to the general population.”

She feels that poverty may be a factor, as low socioeconomic status has been linked with both mental illness rates and increased injury risk, due to things like living in unsafe housing.

Daumit believes that more research needs to be done on these links – mental illness, cancer, and injury risk – and in screening methods for these populations. She thinks that medical professionals also need to do their best to increase screening methods and lower rates of smoking for these groups of people.

The findings establishing a link between cancer and mental illness has been published in Psychiatric Services.

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