Feeling really angry or anxious can greatly increase your risk of having a heart attack, especially if you feel so tense that you clench your fists, a new study reports.

Researchers in Australia found that people's risk of having a heart attack is 8.5 times higher during the two hours following an episode of intense anger, compared with when people feel less angry.

Anxiety is even more threatening, the researchers found. People's heart attack risk is 9.5 times higher during the two hours following elevated levels of anxiety (higher than the 90th percentile on an anxiety scale) than during times of lower anxiety levels, according to the study. [5 Ways Your Emotions Influence Your World (and Vice Versa)]

The findings support anecdotal stories and earlier studies that suggested that anger may trigger heart attacks, and underscores the need for researchers to find ways to protect people who are most at risk for heart attacks, the researchers wrote in their study, published online Feb. 23 in the European Heart Journal: Acute Cardiovascular Care.

For the study, the researchers looked at 313 patients who had heart attacks and were treated at the Royal North Shore Hospital in Sydney, Australia, from 2006 to 2012. Once the patients were feeling better, they answered a questionnaire about the 48 hours before they felt heart attack symptoms.

Using a 7-point scale, the patients rated themselves from "calm" up to a 7, described as "enraged, out of control, throwing objects, hurting yourself and others." The patients also reported what triggered their anger, including arguments with family members or other people, and anger related to work or driving.

Seven of the study participants, or 2.2 percent, had reached what the researchers called "acute levels" of anger within the two hours before they noticed their heart attack symptoms. One person reported feeling acute anger within four hours before the heart attack, and five people said they felt moderately angry within two or four hours before feeling symptoms.

The idea that psychological factors play a role in heart problems is increasingly gaining acceptance among researchers, the study said. The new findings are consistent with previous research by other groups, but unlike many of those earlier studies, the researchers of the new findings verified that all of the study's participants did, in fact, have heart attacks.

The study's lead researcher, Dr. Thomas Buckley, added that "the absolute risk of any one anger episode triggering a heart attack is low," but "our data demonstrates that the danger is real and still there."

Anger management

It's likely that the increased risk of a heart attack following intense anger and anxiety is "the result of increased heart rate and blood pressure, tightening of blood vessels, and increased clotting, all associated with triggering of heart attacks," said Buckley, a senior lecturer and researcher at the University of Sydney and Royal North Shore Hospital.

But both anger and anxiety can be managed with treatment. Doctors should take episodes of anger or anxiety into account when treating a person with heart disease, Buckley said.

People can be trained in ways to reduce their stress and limit their anger and anxiety, or they can avoid the activities that usually prompt such intense reactions, Buckley said. "And for those at very high risk, one could potentially consider protective medication therapy at the time of or just prior to an episode, a strategy we have shown to be feasible in other studies," he said.

Minimizing other risk factors, such as hypertension or smoking, can also help lower risk for heart attack, Buckley said.

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