Recent studies conducted at the San Francisco VA Medical Center suggest two possible mechanisms for the widely recognized link between depression and adverse outcomes in patients with coronary heart disease: lack of adherence to medication regimens and increased levels of norepinephrine, a stress hormone.
"Patients with depression are more likely to suffer heart attacks and heart failure, and more likely to die of heart disease, and no one knows why," notes Mary Whooley, MD, a staff physician at SFVAMC and the principal investigator of both studies. "These results give us two intriguing clues: one behavioral, one biological."
One study looked at the association between depression and self-reported medication adherence in 940 patients with stable coronary heart disease, 204 of whom were diagnosed as depressed. Fourteen percent of the depressed patients reported not taking their medications as prescribed over a 30-day period, compared with 5 percent of the non-depressed patients.
The study appears in the November 28 issue of Archives of Internal Medicine.
Another study examined 24-hour urinary norepinephrine levels in 598 coronary disease patients, 106 of whom had depressive symptoms. A total of 9.4 percent of the depressed participants had a urinary norepinephrine value above the normal range, compared with 3.3 percent of the non-depressed participants. In addition, the more depressive symptoms a participant had, the higher the participant's norepinephrine levels.
This paper appears in the November 2005 issue of the American Journal of Psychiatry.
Neither study indicates a mechanism for adverse coronary outcomes "because we were only looking at cross-sectional data," stresses Whooley, who is also an associate professor of medicine at the University of California, San Francisco.
However, she says, both papers suggest further avenues of research.
The medication-adherence study raises the possibility that because they're depressed, patients simply aren't doing what they're supposed to do to take care of themselves, and this in turn implies a potential treatment, according to Whooley. "If you get rid of the depression, you might get rid of the non-adherence."