Study contradicts doctors' assumption that depression causes post-operative mental decline

May 6, 1997
Media Contact: Michael Purdy
Phone: (410)955-8725

Contrary to what doctors and patients have long believed, coronary bypass surgery per se is not the usual cause of depression found in some patients after surgery, according to a new study from researchers at Johns Hopkins Medical Institutions and the Krieger Mind-Brain Institute.

Patients depressed after bypass and other cardiac surgery were likely to have been depressed before surgery. The study also found a chance that surgery could improve a patient's mood, a finding doctors called "unsurprising" in light of the physical improvements created by surgery.

However, the new finding opens a hole in patients' and doctors' understanding of the mental effects and risks of the operations.

"Research has shown that anywhere from 25 to 80 percent of cardiac surgery patients experience postoperative declines in their mental abilities--problems with memory, verbal skills or physical coordination," explains Guy McKhann, M.D., director of the Mind-Brain Institute. "When they see this in their patients, doctors have typically blamed it on depression triggered by surgery. That's understandable, because serious depression can affect mental abilities. But our study found that surgery and depression are not causally linked."

Hopkins and Krieger researchers studied 124 patients scheduled for coronary artery bypass grafting, giving them a standard test for depression before surgery and one month and one year after surgery. Only 12 patients not depressed before surgery were depressed at one month afterward, and at one year the total declined to 8. Neither is a statistically significant difference, according to Louis Borowicz, also an author on the study.

Hopkins researchers also tested several mental functions, including memory of words and pictures, language skills, ability to pay attention, and physical coordination.

There was little relationship between changes in patients' scores on tests of mental ability and the test for depression.

"Depression is clearly not causing changes in mental ability, so we're still not sure what's behind this phenomenon," says Borowicz. "The average age of patients is increasing, and that can increase the risk for mental decline, but that alone can't account for what we're seeing either. We're planning an extended study of the problem."

The Lancet study was funded by the MacArthur Foundation, the Dana Foundation, the Seaver Institute and the AIREN Foundation. Other authors were Maura Goldsborough; Cheryl Enger, Ph.D., assistant professor of oncology; and Ola Selnes, Ph.D., associate professor of neurology.

-- JHMI --
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