This is the first study to examine a history of suicide attempts along with depression as a marker for future mortality from cardiovascular disease. Also, unlike most previous studies of depression and heart disease, the authors examined major depression, which was assessed with a clinical interview based on accepted diagnostic criteria, instead of using questionnaire scores for depression symptoms. The authors suggest that clinical diagnosis may be "a more robust risk indicator."
Use of antidepressants was not included as a risk factor because less than six percent of those with depression or a history of attempted suicide reported their use, and no cardiovascular-related deaths occurred in that subgroup.
The researchers considered the possibility that depressed people may have more lifestyle-related risk factors such as smoking and poor diet. They found a significant link to heart disease risk coming from depression and suicide attempts, even after correcting statistically for unhealthy behaviors.
"Direct physiological effects of depression may play a greater role than lifestyle factors in this young population," the authors write.
Depression may increase risk of heart disease through physiological mechanisms, such as lower heart rate variability and increased cortisol (a stress-related hormone) and inflammation.
"This is a group that normally should be low risk," Vaccarino says. "Studying these individuals more intensively could be important for understanding how depression affects the heart."
Source: Emory University