People who experience extreme happiness could be at the same risk of heart attacks as those who experience emotional distress.
The condition has been dubbed "happy heart syndrome".
Back in the 1990s, doctors discovered a rare condition called Takotsubo syndrome, or TTS, which linked extreme emotional distress to a potentially fatal weakening of the heart, the Press Association reports.
TTS typically occurs after upsetting episodes such as the death of a spouse or parent, the breakdown of a relationship, or being diagnosed with cancer.
But new research has suggested that the same health outcome can follow happy events too.
Scientists analysed data from 1,750 patients diagnosed with TTS in nine different countries.
Of 485 patients - for whom a definite emotional trigger could be identified - 96% had suffered sad and stressful events such as the loss of a loved one, attending a funeral, being hurt in an accident, or experiencing an illness or relationship problems. One obese patient experienced TTS after getting stuck in the bath.
But in the case of the remaining 20 individuals, heart damage appeared to have been triggered by happy occasions.
These included birthday parties, weddings, surprise celebrations and the birth of a grandchild.
Dr Jelena Ghadri, from University Hospital Zurich in Switzerland, said: "We have shown that the triggers for TTS can be more varied than previously thought. A TTS patient is no longer the classic 'broken hearted' patient, and the disease can be preceded by positive emotions too.
"Clinicians should be aware of this and also consider that patients who arrive in the emergency department with signs of heart attacks, such as chest pain and breathlessness, but after a happy event or emotion, could be suffering from TTS just as much as a similar patient presenting after a negative emotional event.
"Our findings broaden the clinical spectrum of TTS. They also suggest that happy and sad life events may share similar emotional pathways that can ultimately cause TTS."
Takotsubo syndrome causes the heart chamber to balloon out at the bottom while the neck remains narrow. Patients with the abnormality are prone to chest pains and breathlessness, and are at risk of a potentially fatal heart attack.
Scientists are still trying to understand the mechanism behind TTS, which is thought to involve links between psychological stimuli, the brain, and the cardiovascular system.
In the study, 95% of both "broken heart" and "happy heart" patients were women. The average age of the "broken" group was 65 and of the "happy" group 71.
Co-author Dr Christian Templin, from University Hospital Zurich, said of the study: "Perhaps both happy and sad life events, while inherently distinct, share final common pathways in the central nervous system output, which ultimately lead to TTS."
The findings are published in the European Heart Journal.
