European researchers said that people who have outbursts of anger are at greater risk of having a heart attack or stroke in the two hours immediately after the episode.
The study -- a big review of published papers -- is the first to give powerful statistical backing to suspicions that strong emotions can drive cardiac risk, although the underlying biological causes remain unclear.
In the two hours immediately after an angry outburst, an individual's risk of myocardial infarction or acute coronary syndrome rose nearly five-fold, to 4.7 percent, compared to times when the person was calm, the study found.
The risk of stroke tripled, to 3.6 percent, it also found. There were also higher risks for arrythmia, or an erratic beating of the heart.
The risks rose proportionately if the person had a history of cardiovascular problems or was frequently angry.
"Although the risk of experiencing an acute cardiovascular event with any single outburst of anger is relatively low, the risk can accumulate for people with frequent episodes of anger," said Elizabeth Mostofsky at the Harvard School of Public Health in Massachusetts.
"This is particularly important for people who have higher risk due to other underlying risk factors or those who have already had a heart attack, stroke or diabetes.
"For example, a person without many risk factors for cardiovascular disease, who has only one episode of anger per month, has a very small additional risk, but a person with multiple risk factors or a history of heart attack or stroke, and who is frequently angry, has a much higher absolute excess risk accumulated over time."
- Risk rises with anger episodes -
The researchers calculated that one extra heart attack per 10,000 people per year can be expected among people with low cardiovascular risk who are angry only once a month.
This rises to an extra four per 10,000 people with a high cardiovascular risk.
Among people who were frequently angry, five episodes of anger a day would result in some 158 extra heart attacks per 10,000 people with a low cardiovascular risk per year.
The tally would increase to around 657 extra heart attacks per 10,000 among those with a high cardiovascular risk.
The paper, published in the European Heart Journal, looked at nine previously published studies covering wide groups of people whose anger profile was known.
The data trawl found more than 5,000 cases of heart attack and at least 800 of stroke.
The methodology used in these published papers varied, but an unmistakeable association emerged from all of them, the authors said.
Previous attempts to clarify the question were based on small sample sizes where few patients reported having outbursts of anger, they said. As a result, the picture was fuzzy or lacked credibility.
The paper was not designed to explore why anger is so clearly linked to heart attack.
The authors point to previous research which found that psychological stress increases heart rate and blood pressure. Changes in blood flow can cause blood clots and may stimulate an inflammatory response from the immune system.
Further research is needed to pinpoint this mechanism and to finetune options for doctors mulling whether the best treatment should be drugs to lower cholesterol or blood pressure or psychological help or physical exercise to curb dangerous anger episodes -- or perhaps a combination.
In an independent commentary, US specialists Suzanne Arnold and John Spertus from the University of Missouri and Brahmajee Nallamothu of the University of Michigan said the findings called for an all-round approach.
"Treating anger in isolation is unlikely to be impactful," they wrote in the journal.
"Instead, a broader and more comprehensive approach to treating acute and chronic mental stress, and its associated psychological stressors, is likely to be needed to heal a hostile heart."