Feeling constantly stressed could increase your risk of heart and circulatory disease, according to news coverage. But is there truth behind the headlines?

Feeling stressed all the time could raise your risk of heart attack and stroke, according to a new study.

The research, which is published in The Lancet, which has received widespread media coverage, claims to show for the first time how stress could be linked to heart and circulatory disease in humans. 

Constant stress has been linked to higher activity in an area of the brain linked to processing emotions, and an increased likelihood of developing heart and circulatory disease.

The researchers, from Harvard University, suggested stress could be as important a risk factor as smoking or high blood pressure.

The research was made up of two studies. The larger study, made up of 293 people, looked at their brain scans, and suggested that when you are stressed, your amygdala (an area of the brain that deals with stress) signals to the bone marrow to produce extra white blood cells.

This in turn causes the arteries to become inflamed. We already know that inflammation is involved in the process that leads to heart attacks, angina and strokes.

When you experience stress, the amygdala sends a distress signal to your hypothalamus, which then communicates this to the rest of your body so it is ready to fight or for flight.

This could lead to ensuring that patients who are at risk are routinely screened and that their stress is managed effectively

In the first (larger) study, the researchers found that the link between activity in the amygdala and later heart events and stroke was due to increased bone-marrow activity and arterial inflammation.

The second (smaller) study looked specifically at inflammation of the arteries and activity in the amygdala in highly stressed people, and again found an association between raised amygdalar activity and more arterial inflammation. People who rated themselves as more stressed were also more likely to have higher levels of activity in the amygdala.

These processes had been previously shown in mice, but never before in humans, the researchers said.

The BHF view

Emily Reeve, Senior Cardiac Nurse at the British Heart Foundation, said: "The link between stress and increased risk of developing heart disease has previously focused on the lifestyle habits people take up when they feel stressed such as smoking, drinking too much alcohol and overeating.

"Exploring the brain’s management of stress and discovering why it increases the risk of heart disease will allow us to develop new ways of managing chronic psychological stress.

"This could lead to ensuring that patients who are at risk are routinely screened and that their stress is managed effectively," she said.

Limitations

The study was relatively small (293 people) Of these, 22 people experienced heart or circulatory events during follow up – so the findings are based on quite a small number of people. The larger study used previously collected data, based on participants who had been screened for other reasons, mainly cancer. Although the participants had to have been cancer-free for at least one year before their brain scans were taken, this could potentially have affected the results. 

For the smaller study 13 people were chosen who had an ‘increased burden of chronic stress (i.e. history of post-traumatic stress disorder)’ the report says. However, a lot of people who feel stressed in the UK will not experience stress to at such a high level.

Coverage

The story was widely covered in the Daily Mail, The Telegraph, and BBC News as well as on the Today Programme and BBC Breakfast.

Overall, the coverage was quite accurate.

The evidence was made up of two studies but some of the coverage didn’t make it clear that there were two studies, rather than one larger study.

The Telegraph’s headline ‘Scientists finally discover how stress causes heart attacks and strokes’ is misleading, as the researchers say they have established a ‘link’ between brain activity in a certain area and subsequent cardiovascular disease, not a cause and effect. This study only begins to understand this and further research is needed before any conclusions can be made.