SATURDAY, April 2 (HealthDay News) -- Men taking antidepressants may be at risk for atherosclerosis, which can increase the risk of a heart attack or stroke, a small, preliminary study suggests.

Antidepressants were associated with about a 5 percent increase in the thickness of the large artery in the neck called the carotid artery, which carries blood to the brain, the researchers from Emory University found.

Yet experts not involved with the study noted that it did not prove a cause-and-effect relationship between antidepressant use and heart trouble, and added that depression itself can increase the risk of cardiovascular problems.

"Antidepressant medications may decrease cardiovascular risk by treating depression," said Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles.

Since the new findings are very preliminary, Fonarow said, "Patients should not be concerned or stop taking antidepressant medications on the basis of this study."

Results of the research were scheduled to be presented Saturday at the American College of Cardiology's annual scientific session, in New Orleans. Experts note that studies presented at medical conferences do not undergo the same vetting as research published in peer-reviewed journals. The study was funded by the U.S. National Institutes of Health.

For the study, a team led by Dr. Amit Shah, a cardiology fellow at Emory, collected data on 513 middle-aged male twins who were part of the Vietnam Era Twin Registry. Sixteen percent of the men were taking antidepressants, and of these, 60 percent were taking selective serotonin reuptake inhibitors (SSRIs), such as Prozac, Lexapro and Zoloft. The others were taking older antidepressants.

To try to isolate the effect of antidepressants on blood vessels, the researchers measured the thickness of the carotid artery -- called carotid intima-media thickness. The study authors found that a twin taking an antidepressant had a greater intima-media thickness than a brother not taking the drugs.

The finding held true, regardless of the antidepressant taken, the researchers said.

"There is a clear association between increased intima-media thickness and taking an antidepressant, and this trend is even stronger when we look at people who are on these medications and are more depressed," Shah said in a news release from the American College of Cardiology.

"Because we didn't see an association between depression itself and a thickening of the carotid artery, it strengthens the argument that it is more likely the antidepressants than the actual depression that could be behind the association," he added.

The findings also held true after compensating for such factors as age, diabetes, blood pressure, current or previous smoking, cholesterol and weight. Other factors weighed included depressive symptoms, history of major depression and heart disease, alcohol and coffee use, statin use, physical activity, education and employment, the researchers said.

Since each additional year of life is associated with a small increase in intima-media thickness, a brother taking antidepressants is physically 4 years older than the brother not taking antidepressants, Shah's team contended. They also said that even a small increase in intima-media thickness can increase the risk of a heart attack or stroke by 1.8 percent.

It's not clear why there might be an association between antidepressant use and heart disease, the study authors noted. These drugs increase levels of the brain chemicals serotonin and norepinephrine, which are often low in depressed individuals.

Shah said increased levels of these chemicals may cause blood vessels to tighten, and this may lead to reduced blood flow to organs and higher blood pressure, which is a risk factor for atherosclerosis.

Commenting on the study, Dr. Dominique L. Musselman, an associate professor of clinical psychiatry at the University of Miami Miller School of Medicine, underscored that the findings show an association between antidepressant use and atherosclerosis, but not a cause-and-effect relationship.

"This finding is somewhat counterintuitive since it is well known that SSRIs enhance a tendency to bleed," she said, adding that more rigorous studies are needed to see if a cause-and-effect relationship exists.

Musselman also strongly advises patients not to stop taking antidepressants based on this study. Not treating depression can have serious consequences for quality of life, survival after a heart attack or other cardiovascular events, she said.

"This is an important finding that needs to be replicated," she added.

More information

For more on antidepressants, visit the U.S. National Library of Medicine.