Sadness can weigh on you quite dearly, and sometimes a particularly sad or stressful event can trigger what's known as "broken heart syndrome."

Under this condition, also known as Takotsubo syndrome or stress cardiomyopathy, the heart muscles rapidly and severely weaken. This temporary ailment causes severe chest pain and can lead to life-altering consequences such as heart attack and even death.

But it's not just the terrible times that can cause this syndrome; joyful and happy occasions also can trigger broken heart syndrome, according to a study published Thursday in European Heart Journal.

A broken heart can kill you. But maybe so can a happy one.

The researchers analyzed data from the International Takotsubo Registry at the University Hospital Zurich in Switzerland and looked at 485 patients from nine countries who had a specific emotional trigger for the syndrome.

The vast majority - 465, or 96 percent - had broken heart syndrome triggered by sad and stressful events. That included the death of a loved one, an accident, attending a funeral, worries about illness and relationship problems. Think about the stories you hear of a widow or widower who dies soon after a spouse.

But an additional 20 people in the study (4 percent of the group) had the syndrome triggered by joyful occasions, such as a birthday party, wedding, the birth of a grandchild and even a favorite sports team winning. The researchers dubbed them "happy heart" cases.

Now that's quite a small number. Sadness still is much more likely to trigger TTS than joy, and long-term stress can be bad for your health. Stress has a direct link to cardiovascular health (although recent research has called into question the direct impact of unhappiness on mortality).

But the researchers of this new study say their findings "broaden the clinical spectrum" of the syndrome, and that clinicians should be aware of this when treating patients with symptoms.

"We have shown that the triggers for TTS can be more varied than previously thought," study author Jelena Ghadri, a cardiologist at the University Hospital Zurich, said in a release. "A TTS patient is no longer the classic 'broken hearted' patient, and the disease can be preceded by positive emotions too. "

While TTS symptoms are similar to a heart attack - chest pain, shortness of breath, low blood pressure - TTS is very different from a heart attack, most of which are caused because of blockages and clots in the coronary arteries.

Most TTS patients don't have severe blockages and have normal coronary arteries. Their heart cells are "stunned" by stress hormones. The heart takes on unusual, pot-like shape, while a part of it enlarges and doesn't pump blood well. But the rest of the heart functions normally or more forcefully.

Broken heart syndrome most commonly affects women around 60, and that's what played out in this recent study; women comprised 95 percent of the cases analyzed.

The exact mechanisms at play when happy or sad events trigger the syndrome are still not fully known. More research will be needed in this area, author Christian Templin, a cardiologist at the University Hospital Zurich, said in a release. But they have some ideas about what joy and sorrow share in common.

"We believe that TTS is a classic example of an intertwined feedback mechanism, involving the psychological and/or physical stimuli, the brain and the cardiovascular system," Templin said. "Perhaps both happy and sad life events, while inherently distinct, share final common pathways in the central nervous system output," which may lead to the heart syndrome.

The happiness and sadness may share the same pathways is not an entirely novel idea. For centuries, artists and poets have reflected upon the inextricable link between these two seemingly opposite forces. Take Khalil Gibran's "The Prophet," in which the protagonist is asked to expound upon sorrow and joy:

Your joy is your sorrow unmasked.

And the selfsame well from which your laughter rises was oftentimes filled with your tears.

And how else can it be?

The deeper that sorrow carves into your being, the more joy you can contain.

Is not the cup that holds your wine the very cup that was burned in the potter's oven?

And is not the lute that soothes your spirit, the very wood that was hollowed with knives?

When you are joyous, look deep into your heart and you shall find it is only that which has given you sorrow that is giving you joy.

When you are sorrowful look again in your heart, and you shall see that in truth you are weeping for that which has been your delight.

Some of you say, "Joy is greater than sorrow," and others say, "Nay, sorrow is the greater."

But I say unto you, they are inseparable.

Together they come, and when one sits alone with you at your board, remember that the other is asleep upon your bed.