People with mental disorders develop cancer at younger ages and have higher odds of later being diagnosed with certain cancers, including tumors of the brain and lung, according to a new analysis of insurance claims.

“This work is the first of many steps in understanding mental health and cancer … in insured Americans seeking mental and physical health care,” says study author Caroline P. Carney, M.D., of the departments of psychiatry and internal medicine at Indiana University School of Medicine and a research scientist at the Regenstrief Institute in Indianapolis.

A number of previous studies focused on the potential relationship between cancer and mental health disorders such as depression and schizophrenia, but their findings were inconclusive.

Carney and colleagues examined five years’ worth of medical claims for more than 700,000 adult cancer patients living in the Midwest, about 10 percent of whom had submitted mental health claims at least six months before they submitted a cancer claim. The authors excluded patients who submitted a mental health claim after a cancer diagnosis, in case the cancer diagnosis had influenced their mental health.

The cancer patients who had submitted mental health claims were more likely than those who hadn’t to be diagnosed with respiratory and brain tumors during the study period. They also were diagnosed with cancer at significantly younger ages than the average — two years earlier for men and three years earlier for women. Female mental health claimants had higher odds of being diagnosed with leukemia and lymphoma.

The results are published in the current issue of the journal Psychosomatic Medicine.

Carney and colleagues said they were not surprised by the higher rates of respiratory tumors among the mental health claimants. This finding is likely related to higher smoking rates among people with mental disorders like depression and has been noted in other studies. Because of the nature of insurance claims, Carney and colleagues were not able to directly adjust for the effect of smoking.

“Both mental health workers and primary care providers should stress smoking cessation programs,” Carney notes.

That brain tumors were more common in patients with psychiatric conditions suggests that some brain tumors “may be present and causing mental symptoms well ahead of other neurological symptoms leading to diagnostic evaluations,” Carney says. “It is unlikely that mental disorders cause brain tumors per se. It is more likely that the earliest symptoms of brain tumors are mental, not neurological.”

This finding suggests “people presenting with new mental symptoms at times of life atypical for a new onset of a psychiatric condition should undergo evaluation for the presence of a brain tumor,” Carney says.

Carney and colleagues note several study limitations. One is that as mental health conditions tend to be underdiagnosed, those study participants with psychiatric conditions who did not submit claims may have skewed the study results. Also, given the mostly white population of the Midwest, the study results may not be applicable to other ethnicities.