Here's something for grumps to be happy about: Being unhappy is not going to shorten your life.

Research published in the well-known medical journal Lancet debunks the widespread belief that happy people live longer. Using data from 720,000 women between 50 and 69, scientists found no link between glumness and mortality. Ditto for happy-go-lucky types.

The study, funded by the UK Medical Research Council, followed the women over 10 years, taking note of who died and the cause of death in each case.

Conventional wisdom, based on a slew of other studies, was that a sunny disposition can protect against heart disease and other serious health problems. But the scientists behind the new research say that the previous studies were flawed because they didn't consider that poor health itself can cause unhappiness. Not the other way around.

And of course, poor health can lead to death.

"After allowance for these associations our large prospective study shows no robust evidence that happiness itself reduces cardiac, cancer, or overall mortality," the authors wrote.

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