A new study has revealed a link between serious mental illness and cancer risk. People suffering from schizophrenia, bipolar disorder and disabling depression are 2.6 times at higher risk of developing cancer than the general population.
The study's findings raise questions about whether patients burdened with serious mental illness are receiving appropriate cancer screenings and preventive care related to risk factors for cancer, such as smoking.
"The increased risk is definitely there, but we're not entirely sure why," says study leader Gail L. Daumit, M.D., M.H.S., an 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," Daumit said.
In a separate study, published online last month in the journal Injury Prevention, Daumit found that people with serious mental illness were nearly twice as likely to end up in a hospital's emergency room or inpatient department suffering from an injury than the general population and about 4.5 times more likely to die from their injuries.
Daumit said that roughly 5 percent of Americans have a serious mental illness, and this group is known to be two to three times more likely to die prematurely than those without disabling psychiatric problems.
A small proportion of the higher risk, she says, can be attributed to the higher risks of suicide and homicide victimization in this population, 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.
Daumit, a practicing internist, speculates that this population is "falling through the cracks."
In the first study, Daumit's team looked at data from 3,317 Maryland Medicaid beneficiaries with schizophrenia and bipolar disorder, determining whether they developed cancer between 1994 and 2004 and what type of cancer they had.
They found that 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. There were no racial differences in who developed cancer in this group, whose average age was between 42 and 43 years.
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 speculated 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 said, could be related to lifestyle issues, such as smoking, lack of physical activity and a diet lacking fruits and vegetables.
In the second study, Daumit and her colleagues looked at similar Maryland Medicaid data from 1994 through 2001 in search of other patterns.
They found that 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 types of injuries most frequently experienced by those in the study.
Poisoning and burns were the least frequent types of injuries. 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.
"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.
The study's findings were recently published in the journal Psychiatric Services.