Unhappiness may lead to bad choices, but it won't kill you

At the start of the study, 39% said they were happy most of the time, and another 43% described themselves as usually happy

Even though poor health is a known cause of unhappiness, and bad lifestyle choices often follow bad moods, misery alone probably won't kill you, a UK study suggests.

"We found that after accounting for poor health and other lifestyle choices, being happier doesn't make you live longer, and being stressed doesn't increase your risk of death," said lead study author Bette Liu of the University of New South Wales.

To explore the connection between unhappiness and the likelihood of dying, Liu and her colleagues looked at data on more than 700,000 middle-aged women collected over more than a decade. At the start, when the women were around 59 years old, 17 per cent reported being unhappy, and this was more likely in women who were in poor health. During the next ten years, about 31,500 women died, representing about four per cent of the study population.

After researchers adjusted for a host of factors independently linked to mortality - like hypertension, diabetes, smoking, drinking, asthma, arthritis, depression and anxiety - mere unhappiness wasn't associated with increased mortality from all causes, or specifically from cancer or heart disease.

The data was collected from 1996 to 2001. When they joined the study, and again every three to five years, women completed questionnaires asking about social and demographic factors, lifestyle choices and health.

At the start of the study, 39 per cent said they were happy most of the time, and another 43 per cent described themselves as usually happy. Researchers counted as "unhappy" the 16 per cent of women who were happy only sometimes and the one per cent who said this was a rare occurrence.

Over time, few women changed their assessment of their own happiness levels, the researchers report in The Lancet.

Generally, the happy women in the study were older, less likely to have advanced degrees and more likely to be non-smokers as well as regular exercisers with steady romantic relationships who routinely participated in religious or other group activities. These happy women were also more likely to get eight hours of sleep each night.