People who carry the "stress gene" have a 38 percent higher risk of heart attack or even early death, a new study has reported.

The study, conducted by researchers at Duke Medicine, explains why some people are at an increased risk of suffering from heart diseases.

Stress sets off a cascade of chain reaction in the body. During a negative situation, serotonin is released in the brain. This chemical then signals the release of stress hormones.

Previous research had identified a change of one letter in the genetic code (single nucleotide polymorphism, SNP) on a gene that makes serotonin receptor. This variation leads people to overreact to stress.

Researchers had earlier found that men with a certain genetic variant had twice the levels of cortisol in their bodies than other people without the variation. Cortisol is produced in the body as a primary response to stress.

"It is known that cortisol has effects on the body's metabolism, on inflammation and various other biological functions, that could play a role in increasing the risk of cardiovascular disease," said lead author Beverly H. Brummett, Ph.D., associate professor of Psychiatry and Behavioral Sciences at Duke, according to a news release. "It has been shown that high cortisol levels are predictive of increased heart disease risk. So we wanted to examine this more closely."

For the present study, the scientists conducted genetic analyses of over 6000 people with a history of heart diseases. All participants were white and at least two-thirds of them were males. Researchers found that 13 percent of the participants carried the genetic variation.

The team also found that patients with the variation had higher chances of heart attacks. Even after adjusting for other factors such as smoking or diet, these people had 38 percent more risk of suffering from heart attack or even an early death.

Researchers haven't found how the variant increases heart attack risk. They said that they will explore how this variation can be targeted to reduce stress and heart disease risk in patients.

The study is published in the journal PLOS One.