Being fiery and expressing negative emotions is the key to long-lasting good health, according to researchers at the University of Jena in Germany.
The study assessed more than 6,000 patients and found that those who internalised their anxiety suffered from a raised pulse, the 'Daily Mail' reported.
Over time this results in high blood pressure and an increased chance of developing a wide range of illnesses, from coronary heart disease to cancer and kidney damage.
Researchers identified a group of so-called 'repressors' who were particularly at risk.
"These people are distinguished by the way that they attempt to conceal outward signs of fear, and also by their defensive behaviour," researcher Marcus Mund said.
"They avoid risks and always seek a high level of control over themselves and their surroundings," Mund said.
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"For instance, when exposed to a stressful task they exhibit a higher heart rate and pulse ratio than non-repressors and show other objective signs of stress and anxiety," Mund said.
Although they might be at a higher risk of developing certain illnesses, recovery from a range of conditions appears to be faster among repressors.
"Because of their need for control, repressors are very disciplined and more motivated to adapt their lifestyles," said Mund.
The study was published in the journal Health Psychologies.