Panic attacks may have an impact on the heart
People who suffer from panic attacks have a higher risk of going on to develop heart disease, say scientists.
The research, in the European Heart Journal, found heart attacks were a third more likely in people under 50 with panic disorders.
The University College London researchers said panic disorders might trigger nervous system changes which could help clog arteries.
But others suggested panic attacks might trigger unhealthy behaviour.
The study looked at the health records of more than 400,000 people across a wide range of ages, including 57,615 people who had been diagnosed with panic attacks.
The under 50s in this group were 38% more likely to have a heart attack and 44% more likely to develop heart disease compared with those without the condition.
For people aged over 50, the risk of heart disease was still increased, but to a much lesser extent.
Curiously, although the research suggested that people with panic disorders were more vulnerable to heart disease, it found they were less likely to actually die from it.
Dr Kate Walters, who led the research, said little was known about any direct connection between panic attacks and cardiac problems, although attacks could be triggering changes in the nervous system which increased the risk.
"The symptoms of panic attacks can closely mimic those of a heart attack or acute cardiac disease, and it seems there may be a complex relationship between them.
"The findings could be due to several factors, including initial misdiagnosis of coronary heart disease as panic attacks, or due to a true increase in coronary heart disease caused by panic disorder, potentially through activation of the sympathetic nervous system in ways that lead to clogging of the arteries and reductions in the normal variation in heart rate.
"Our findings have significant implications for clinicians."
Dr Walters said one possible explanation for why anxious or panicky people were less likely to die from heart problems was their tendency to visit the doctors more often.
And she stressed that the generally lower rate of heart disease and heart attacks in the under-50s meant that even the substantial percentage increase found by the study amounted only to a small rise in actual risk for each person.
The British Heart Foundation played down the possibility of a direct link between panic attacks and heart problems.
A spokesman said: "There may be many reasons why this association was found. For example people who suffer from panic disorders may be more likely to smoke, or drink too much alcohol to help them relax.
"Having an unhealthy lifestyle is one of the biggest risks to developing heart disease, whether you have panic attacks or not."