But being happy can't make you live longer, either...
We're often told that being happy can make us live longer, and that unhappiness could kill us faster - but according to a new study, happiness and unhappiness do not have an impact on the longevity of our lives.
The study, carried out by Oxford University researchers and published in the Lancet medical journal, found that while poor health does make people unhappy - and also makes them live shorter lives - unhappiness in itself is not life-shortening.
They indicated that previous studies suggesting this were not taking into account the unhappiness that is often caused by poor health.
'Illness makes you unhappy, but unhappiness itself doesn’t make you ill,' Dr Bette Liu told The Guardian. 'We found no direct effect of unhappiness or stress on mortality, even in a 10-year study of a million women.'
As part of the UK Million Women study, women filled in questionnaires about their lives, health, stress levels, feelings of control, relaxation levels and happiness, and are still being followed up on in 2015.
Co-author Prof Sir Richard Peto told the paper: 'The claim that this [unhappiness] is an important cause of mortality is just nonsense. Compare it with light smoking, where, if you smoke five to 10 a day, you are twice as likely to die in middle age.'
He pointed out that those who are unhappy may indulge in life-shortening activities such as eating or drinking too much or harming themselves. 'But if you ask does [unhappiness] of itself have any direct effect on mortality, it doesn’t,' he said.
The study found that women were more likely to be happy if they were older, less deprived, physically active, non-smoking, with a partner, religious, social and regularly getting adequate sleep.
'Many still believe that stress or unhappiness can directly cause disease, but they are simply confusing cause and effect,' said Peto. '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.'
What do you think of the findings? Let us know @marieclaireuk
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