CHAPEL HILL -- A new study at the University of North Carolina at Chapel Hill will look at the effects of antidepressant drugs on the heart's response to stress.
"We know that people who are depressed early in life develop cardiovascular complications later on," said Patricia Straneva, graduate student in psychology at UNC. "We also know that cardiac patients with depression are more likely to die from their heart disease than non-depressed patients. But we don't really know why there is such a strong relationship between heart disease and depression, primarily because we don't really know what the mechanism is that causes depression in the first place. However, we do know that people who are depressed have significantly elevated levels of stress hormones.
At the university's Stress and Health Research Program, heading the study with Straneva is Susan Girdler, Ph.D., assistant professor of psychiatry at UNC-CH School of Medicine. She said their project focuses on two widely used anti-depressants -- bupropion and paroxetine.
"These drugs are known to affect different physiological systems in the body. If we find that one of them influences cardiovascular stress responses differently than the other, then the study results may have special implications for the treatment of heart patients with depression."
Wellbutrin works against depression by potentiating the body's noradrenergic mechanisms, including release of the hormone norepinephrine. Paroxetine is in a class of antidepressants that enhance the availability of serotonin in the brain. Both norepinephrine and serotonin influence mood and the cardiovascular system.
The study will test two categories of volunteer participants: (1) individuals with no current or past history of any psychiatric disorder and (2) individuals currently under treatment for depression with either bupropion or paroxetine. Participants in the second group will have been taking their antidepressant for at least two months. All subjects will be otherwise medically healthy.
A psychiatric examination will rule out other mental disorders. "We're trying to verify that the people who are depressed don't also have a clinical diagnosis for anxiety or any other psychiatric disorder that might confound the cardiovascular variables we're looking at," Straneva said.
Testing will then involve a 24-hour ambulatory blood pressure monitoring. For one day, participants will wear a blood pressure monitor that will provide blood pressure and heart rate throughout the person's normal activities. Urine samples taken throughout the day will be tested later for stress-related chemicals.
On a separate day, a 3-hour laboratory session will include blood pressure and electrocardiogram (EKG) monitoring during stress situations such as an ice pack applied to the forehead, mental arithmetic test, and speech test. Blood samples will be measured for the stress-related hormones epinephrine, norepinephrine, and cortisol. Qualified participants will receive $200 for participating.
The UNC investigators hypothesize that people taking one of the antidepressants will show the greatest cardiovascular stress response compared to the other groups studied. Over time and continued use of the drug, increased levels of stress hormones and blood pressure may lead to structural and functional cardiac changes that could make the heart not as well equipped to respond to natural stress.
Still, the researchers point out that the findings can only be suggestive of such implications and that a long-term study is needed. "That study will come later," Straneva noted. "Now we're looking at functional differences based on antidepressants. We can then apply the findings to make recommendations about the type of antidepressant treatment we would recommend for cardiac patients."
For details about study enrollment, call 919-966-2544
Note to media: Patricia Straneva and Dr. Susan Girdler can be reached at 919-966-2544; email: stranepa@med.unc.edu
UNC School of Medicine Contacts: Karen Stinneford, 919-966-6047, email kstinnef@unch.unc.edu; Leslie H. Lang, 919-843-9687, llang@med.unc.edu