Oct. 6, 2004 -- People with mental disorders, especially mood problems like clinical depression and bipolar disorder, have a high risk of developing certain cancers at younger ages, including brain and lung cancer, new research shows.
Smoking and alcohol abuse are obvious players in this pattern, both linked with clinical depression and lung cancer in numerous studies, writes lead researcher Caroline P. Carney, MD, MSc, a psychiatrist and internist with Indiana University School of Medicine. Her study appears in the latest issue of the journal Psychosomatic Medicine.
Also, some mental health problems are caused by the cancer. For example, mood disorders like clinical depression have been recognized as an early symptom of brain tumors. The increased pressure in the brain caused by the tumor can cause a variety of symptoms such as seizures or mental disturbances including depression.
Clinical Depression and Cancer
In her study, Carney and colleagues examined the medical claims for about 722,000 adults, filed over a four-year period. Of these, about 72,000 had filed mental health claims. Researchers compared the development of cancer in this group with a separate group who developed cancer but didn't file mental health claims.
Patients whose cancer diagnosis came within six months of their first mental health treatment were not included in the study since some mental health problems are caused by the cancer and not vice versa.
People with mental disorders were no more likely to develop cancer than those without mental disorders. However, people with mental disorders were more likely to develop cancer at a younger age and had more brain and respiratory tumors.
As expected, people with mood disorders like clinical depression had higher odds of developing tobacco-related cancers (cancers of the mouth, throat, and lung), writes Carney. People with mental disorders have high rates of smoking and alcohol abuse -- both of which increase the risk of tobacco-related cancers.
She also found:
- Mood disorders were the most common mental disorder linked to cancer. Thirty-two percent of men and 43% of women with mood disorders developed cancer less than two years after their diagnosis of the mood disorder.
- Seventeen percent of women and 11% of men had anxiety disorders prior to their cancer diagnosis.
On average, both men and women filed their first mental health claim about one year before the cancer diagnosis, writes Carney. Because of this lag time, it appears unlikely that the cancer caused the mental disorder.
Other patterns emerged for men and women with mood disorders.
Women with mood disorders like clinical depression:
- Had higher odds for developing leukemia and lymphoma -- an "unexpected discovery." Even though fatigue and lack of energy are often found with lymphoma -- and could be mistaken for depression -- the time frame for patients in her study eliminated that scenario, she says.
- Were younger than the women in the comparison group when their first cancer claim was filed
- Had higher odds of brain and lung tumors compared with women without mental disorders
Men with mood disorders:
- Were 83% more likely to be diagnosed with a brain tumor after their first mental health claim compared with men in the comparison group
- Were more likely to have more advanced cancer at diagnosis
- Had higher odds for developing brain and lung tumors
Diane Thompson, MD, director of psychiatric oncology at the Winship Cancer Institute at Emory University School of Medicine in Atlanta, was surprised by Carney's findings.
"Often when patients are diagnosed with cancer, they will say, 'I know this started because of some particular stressor -- a change in job, problems with my spouse,'" Thompson tells WebMD.
However, researchers have been unable to show a strong link between stress and cancer, she notes. "There's one exception -- women who have had a long history of chronic clinical depression have a higher risk of dying from breast cancer. This may be due to lack of compliance with treatment."
Also, when a patient has a sudden mood change, psychiatrists are trained to look for "organic" causes of depression, like brain tumors, Thompson says. These patients should receive brain imaging and other tests, she notes.
But with leukemia and lymphoma -- and pancreatic cancer -- one study showed that clinical depression is the primary symptom patients have. "It leads us to wonder if the cancer itself is causing depression, if our body's immune system is picking up on it. It may be same with brain tumors," Thompson tells WebMD.
Carney's study points to a pattern, "but don't jump to huge conclusions," Thompson says.
Nevertheless, anyone who abruptly develops a mood disorder like clinical depression should always see a doctor, she says.