It's said that laughter is the best medicine, but don't expect it to be the fountain of youth, a new study says . Researchers from a large British study say unhappiness and happiness really don't have anything to do with how long you live or how soon you die.

The findings, published in The Lancet, say that while other studies have said happiness increases longevity, it's more likely that poor health -- which can cause unhappiness -- brings higher mortality.

"Illness makes you unhappy, but unhappiness itself doesn't make you ill. We found no direct effect of unhappiness or stress on mortality, even in a 10-year study," study author Bette Liu said in a statement.

The large-scale study included analysis of nearly 720,000 women who were given a questionnaire at the start of the study, asking about their health, happiness and stress levels. Five in six women responded by saying they would normally consider themselves happy.

The women, with a median age of 59, were followed for a decade and researchers looked at those who died from any cause during the follow-up period. These were women free of major disease, like heart disease or cancer.

Their findings? Maybe not what you'd expect. The death rate for the "unhappy" women was no different from those who were generally "happy" women.

"Many still believe that stress or unhappiness can directly cause disease, but they are simply confusing cause and effect," co-author Richard Peto said in a statement. "Of course people who are ill tend to be unhappier than those who are well, but the UK Million Women Study shows that happiness and unhappiness do not themselves have any direct effect on death rates."

While happiness may not help you live longer, other studies have shown that a sense of purpose, rather, can certainly help. A 2014 study in particular said that having a purpose and setting goals to fulfill it, can help you lower your mortality risk, regardless of when you reach your goals.

So consider it good news for grumps -- your bad mood probably won't kill you. And sorry, positive Pollys, your happiness won't save you, either.

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