The relationship between heart disease and stress is well known and generally it's common knowledge that 'stressed out' types tend to be more susceptible to heart problems. In fact, it's even possible for a very stressful situation to become the catalyst for cardiac arrest.
What's less well known generally is precisely how stress and heart disease are linked or how misinformation about this relationship has been spread.
There are many ways in which stress and heart disease are linked and stress can have a direct impact on blood pressure, cholesterol and heart rate.
This is due to the nature of the fight or flight response which is to trigger changes in the body designed to aid optimal physical performance. From an evolutionary perspective stress increases muscle tone, focus and speed in order to help us escape imminent danger.
Thus adrenaline, norepinephrine, dopamine and cortisol are secreted which have those effects and also increase heart rate and vasoconstriction (narrowing of the veins and arteries) to aid circulation to the brain and muscles. This forces the blood around the body faster and harder thus increasing blood pressure and combined with the increase in BPM this can place a lot of extra strain on the heart.
Additionally, the stress response has also been shown to directly increase blood viscosity (1) which could help us were we to be injured while fighting or fleeing by encouraging clots to form in the blood thus preventing bleeding out. Pro-inflammatory cytokines are also produced during the fight or flight response which can affect the entire body.
Over time, arterial construction and high blood pressure can cause damage to the blood vessels as well as plaque build-up. What's more, some research also shows that stress is able to increase bad (LDL) cholesterol too by flooding the body with glucose which can eventually become fat. Stress can also lead to 'comfort eating' which is exacerbated by the effect that cortisol has on hunger.
Through all these mechanisms, stress and heart disease are very closely linked. Stress not only places short-term strain on the heart but also causes further circulatory problems in the long term.
All this is certainly true and demonstrates a strong link between stress and heart disease. However the idea that 'stressed' personality types are more likely to experience heart disease is one that may have been exaggerated for commercial gain by tobacco companies.
The 'Type A and Type B personality theory' claims that people can be categorized into two types: those who are prone to competitive, aggressive and highly motivated behavior (type A) and those who are more likely to be relaxed, placid and reserved (type B). This theory became very popular after it was first suggested, to the point where most people can tell you that they're a 'type A' or 'type B' personality. It's also 'common knowledge' that type A personalities are more prone to heart problems than type B due to their 'always on' nature.
However, some of the research that supports this personality theory has come under serious criticism both for its methodology and its potential bias. This is because a lot of research surrounding the topic was funded by the tobacco industry with the intention of creating a mitigating factor that could shed doubt on the connection between smoking and heart disease.
As a lot of studies had been conducted demonstrating a causal link between smoking and heart disease, tobacco companies allegedly wanted to promote the idea of Type A personalities as being more likely to smoke and more likely to get heart disease. The hope was that this would then be a confounding variable that would render previous research unreliable.
Friedman, who had conducted studies attempting to support the link between type A stress and heart disease, criticized a decision by the US Occupational Safety and Health Administration to restrict indoor smoking claiming that there was insufficient evidence to support a link between smoking and heart problems because previous research did 'not take into account the confounding variable of type A behavior'. This was despite the fact that at the time only 3 out of 12 studies had found support for type A personalities even existing. The only aspect of type A personality that might be a predictor of heart disease according to numerous studies is the 'hostility' dimension.
If all this sounds a little like a cynical conspiracy theory, then bear in mind that attempts were also made to explain the health problems of passive smokers as being the result of 'stress caused by the media for claiming their loved ones were killing themselves'.
So do 'stressed out people' have nothing to worry about with regards to stress and heart disease?
As we saw at the start of this article, there is a clear link between stress and heart disease and stress can cause all manner of issues for your circulatory system in both the long and short term.
That said though, stress is also an unavoidable part of life and is something that almost all of us encounter on a regular basis to some degree. In other words, most people aren't at any risk of suffering a heart attack because they're working to a deadline. Nor is your psychological disposition likely to put you at serious risk of heart problems.
Rather, the take home message is that stress and heart disease are somewhat linked – that stress is one of many different factors that can contribute to heart problems. If you are someone who is already at risk of heart disease, then avoiding stress would definitely be advisable.