We've long since known that too much stress is bad for you, and a large scale study has revealed that experiencing stress can increase the likelihood of a heart attack by almost 50%.
Interestingly, however, the important factor was an individual's perception of stress, said scientists.
People who believed stress was harming their health "a lot or extremely" were more at risk than those who shrugged off its effects.
After taking account of other factors that could influence the result, the increase in risk fell to 49% but remained significant.
Speaking to HuffPost UK Lifestyle, Neil Shah, Director of the Stress Management Society said: "In my opinion, 50% is an underestimate. It's not news that stress is a major contributor to heart disease, strokes, cancer and type 2 diabetes. Six or seven years ago – poor diet was the primary contributor to these diseases, but it has been recognised that you can have terrible of diet and get away with it, but if you have high levels of stress, it's only a matter of time before you have problems. The heart is the first organ in the body that suffers."
Last year, the number of people who needed to be treated for stress had gone up by 7%. Shah says that this isn't an overnight process by something that happens slowly. "The first thing people say is: how did this happen to me. This didn't happen overnight - too much stress is like slowly committing suicide for the last 10 or 20 years and it is directly as a result of the way you’ve been living your life."
Lead investigator Dr Hermann Nabi, from the Inserm medical research institute in Villejuif, France, said: "We found that the association we observed between an individual's perception of the impact of stress on their health and their risk of a heart attack was independent of biological factors, unhealthy behaviours and other psychological factors.
"One of the important messages from our findings is that people's perceptions about the impact of stress on their health are likely to be correct."
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Stress is not a bad thing, says Shah. "We've demonised it but sometimes it's a good thing because in certain situations, it is useful like in fight -or-flight situations. The challenge isn’t getting stressed but in modern life, it's getting stressed when it doesn’t serve us. You need to understand what you can do to break that."
Writing in the European Heart Journal, the authors of the study said their findings had far-reaching implications.
"Our findings show that responses to stress or abilities to cope with stress differ greatly between individuals, depending on the resources available to them, such as social support, social activities and previous experiences of stress," Dr Nabi said.
Shah advises: "Think about what changes you undergo when you’re feeling stressed or overwhelmed. When does it happen and what occurs when it does? What are your strategies? The most common way people cope with it is by eating or drinking sugar or alcohol. Having a tea or coffee doesn't help - it's a stimulant and they actually have the reverse effect because your body is already hyper stimulated.
"Take a break away from your desk. Think about movement. Anyone who has exercised after a long day at work says it makes you better. Refocus your mind. If you start panicking you’ll get more stressed, so use your breath, because stress causes a lack of air going into brain."
Together with colleagues from the UK and Finland, Dr Nabi's team followed the progress of more than 7,000 male and female Whitehall II participants for up to 18 years from 1991.
The civil servants, whose average age was 49.5, were asked to what extent they felt day-to-day stress had affected their health.
They could answer "not at all", "slightly", "moderately", "a lot" or "extremely".
Of the total, just 8% fell into the last two groups who believed their health was severely affected by stress.
Other questions related to perceived levels of stress as well as lifestyle factors such as smoking, alcohol consumption, diet, and exercise.
Medical information on blood pressure, diabetes, and body mass index (BMI) was also collected together with other data such as marital status, age, sex, ethnicity and socio-economic status.
NHS records were monitored to see how many fatal or non-fatal heart attacks occurred in the different groups by 2009.
In their paper, the authors wrote: "Although, stress, anxiety, and worry are thought to have increased in recent years, we found only participants (8%) who reported stress to have affected their health 'a lot or extremely' had an increased risk of CHD (Coronary Heart Disease).
"In the future, randomised controlled trials are needed to determine whether disease risk can be reduced by increasing clinical attention to those who complain that stress greatly affects their health."
Thembi Nkala, from the British Heart Foundation, which part-funded the study, said: "The effect of stress on your body and heart is an extremely complex issue and it's something we don't yet fully understand.
"These findings raise the possibility that the mere perception of stress can impact on heart health - but they also leave more questions than answers.
"We'll need more research to unpick this complicated relationship further but in the meantime it's vital everyone finds ways to unwind and decrease their daily stress levels."
The results are from the Whitehall II study which has monitored the health of several thousand London-based civil servants since 1985.