By Marilyn Elias, USA TODAY

Depression almost doubles the risk of developing heart disease over 12 years, according to a long-term study of twins. The findings are to be reported today at the American Psychosomatic Society meeting in Chicago.

Mounting evidence has found that depression makes people more vulnerable to heart trouble. Recent studies, though, find that some genes that increase the risk of heart disease also may make people more prone to depression, which has raised the question of whether the depression-heart disease link is genetic.

But the twins study, which followed more than 1,200 middle-aged men, teases out the influence of genetics and finds that depression takes a huge toll on the heart that can’t be chalked up to a roll of the genetic dice.

Depression contributes to the risk of heart disease as much as diabetes, high cholesterol or obesity does, says study leader Jeffrey Scherrer of Washington University and the Veterans Affairs Medical Center in St. Louis. None of the men in his study – who were tracked from their early 40s to their mid-50s – had heart disease at the start, and Scherrer controlled for key factors, such as high blood pressure, that can lead to heart problems.

Twins offer a unique way to find out how much genetics influences health because identicals share 100% of their genes, and fraternal twins have 50% of genes in common. The study included both kinds of twins.

“This study tells us you can’t explain away the role of depression in heart disease by saying it’s all due to genetics,” says Jeanne McCaffery, a psychologist at Brown University Medical School who has done gene studies on the question.

There’s no evidence yet that treating depression will make adults less likely to have heart attacks, adds François Lesperance, a psychiatrist at the University of Montreal. He did the pioneering studies linking depression and cardiac problems.

But so much research has confirmed the link that it justifies more vigorous medical monitoring of heart patients with depression, Lesperance says.

He points to one study that showed a brief mental health screening could identify heart patients with depression, who turned out to be less likely to take medication.

“Clearly, they need to be checked up on more often,” he says.

One big hole in research on depression, heart disease and genetics is that study participants are overwhelmingly male, McCaffery says. “It’s very important to look at whether you’d get these effects in women, because we just don’t know.”