Tapping into 40 years of medical data, Johns Hopkins researchers have found that men plagued by depression are twice as likely to have a heart attack or develop heart disease than peers who aren't depressed.
The study, published in today's issue of the Archives of Internal Medicine, confirms what about 10 others have found. But the Johns Hopkins School of Medicine research used better data, including years of cholesterol and blood pressure measurements that enabled scientists to rule out those factors and see depression as the problem.
"Does depression cause heart disease? I think the evidence shows that it does," said Dr. Daniel E. Ford, the study's lead author and an associate professor of medicine, epidemiology, and health policy and management at Hopkins.
The results came from an analysis of data from the Johns Hopkins Precursors Study, a long-term investigation of 1,190 male medical students enrolled in Hopkins between 1948 and 1964. They are still tracked today.
Ford and his colleagues found that after 40 years of follow-up, 12 percent of the men reported suffering at least one episode of clinical depression. These former students were 2.12 times more likely to develop coronary artery disease or suffer a heart attack than their nondepressed peers.
For the 150 women in the study, results were the same. This was after researchers had accounted for other factors such as diabetes, high blood pressure, smoking and high cholesterol.
But science can't explain yet why clinical depression is a risk factor for heart disease.
Some researchers suspect that chemicals such as adrenalin, which are elevated in people with depression, may lead to variability in heart rates. In another theory, patients with depression may be more prone to blood clots. One study found that depressed people who weren't treated with medications had stickier platelets.
This is a key question for investigation. Another puzzle that must be solved, doctors said, is to what extent treatment of depression reduces the risk of heart disease.
Mental health advocates warned that depression is not being taken seriously enough by modern medicine. One recent report discovered that a third of adults with major depression who saw their primary care doctors remained undiagnosed for at least a year.
