Serious mental illness drives up cancer risk

JOHNS HOPKINS (US) — People with serious mental illness such as schizophrenia and bipolar disorder are more than twice as likely to develop cancer than the general population.

The findings, published in July’s issue of the journal Psychiatric Services, raise questions about whether patients burdened with serious mental illness should receive more cancer screenings and preventive care related to risk factors, such as smoking.

“The increased risk is definitely there, but we’re not entirely sure why,” says study leader Gail L. Daumit, associate professor of medicine and psychiatry at the Johns Hopkins University School of Medicine. “Are these people getting screened? Are they being treated? Something’s going on.”

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In a separate study, published online in June by the journal Injury Prevention, Daumit also found that people with serious mental illness were nearly twice as likely as the general population to end up in a hospital’s emergency room or inpatient department with an injury—and about 4.5 times as likely to die from their injuries.

Daumit says roughly 5 percent of Americans have a serious mental illness; that group is known to be two to three times more likely to die prematurely than those without disabling psychiatric problems.

Some of the gap, she says, can be attributed to the higher risks of suicide and homicide victimization, but those factors do not account for most of the disparity. The top causes of death are cardiovascular disease and cancer, the same top causes of death for those without serious mental illness.

Cancer and smoking

In the cancer-related study, Daumit’s team looked at data from 3,317 Medicaid beneficiaries from Maryland with schizophrenia and bipolar disorder, determining whether they developed cancer—and, if so, what type—between 1994 and 2004. Overall, the mental patients were 2.6 times as likely as the general population to get cancer, but the differences for some types of cancer were even more striking.

Patients with schizophrenia, when compared to the general population, were more than 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. People with bipolar disorder experienced similarly high risk for lung, colorectal, and breast cancer.

Daumit says one reason for the elevated risk of lung cancer could be smoking, which is more prevalent in people with serious mental illnesses. She also speculates that the breast cancer risk could be related to the fact that women with schizophrenia and bipolar disorder are less likely to have children, and childbearing is believed to reduce breast cancer risk.

Also, some psychotropic medications can increase levels of the hormone prolactin, a factor that has been linked to breast cancer. The colorectal cancer risk, she says, could be related to lifestyle issues, such as smoking, lack of physical activity and a diet lacking fruits and vegetables.

Daumit says more study is needed on the role of behavioral and pharmacological factors in increased cancer risk among people with serious mental illness, and the extent to which this population receives appropriate cancer screening and treatment.

She says mental health providers and primary care physicians must work together to promote screening as well as to reduce modifiable risk factors such as smoking in mental health patients.

Risk for injury

In the injury study, Daumit and her colleagues looked at similar Maryland Medicaid data from 1994 through 2001 in search of other patterns. Over the seven-year period, 43 percent of the 6,234 people with serious mental illness in the group studied were seen at a hospital emergency department or admitted with an injury. Among the members of the study group with any injury, 42 percent were injured once, 23 percent twice, 25 percent three to five times and 10 percent six or more times.

Superficial injuries, open wounds and sprains were the injuries most frequently experienced by those in the study. Poisoning and burns were the least frequent.

Daumit says the results suggest that people with serious mental illness appear to be at heightened risk for both intentional and unintentional injury, and the types of injuries are mostly consistent with falls and minor violence.

People with serious mental illness are more likely to have substance abuse problems, and being under the influence of drugs or alcohol can increase injury risk, as can being in a location where illegal drugs are sold, Daumit says. But substance abuse rates don’t explain all of the increased risk, she says.

Another factor that may be at play, she says, is low socioeconomic status, which is also associated with mental illness and injury risk. Environmental risk factors related to poverty include unsafe housing (without appropriate railings to prevent falls, for example) and poorly maintained neighborhoods (such as those lacking sidewalks).

“Just as this population has other medical risks, injury requiring acute medical attention in the emergency department is common and we should consider this when we are looking at the overall care of the patient,” Daumit says.

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