About 39 percent reported being happy most of the time, 44 percent usually happy and 17 percent unhappy.
At the beginning of the study, those who perceived they had poor health were much more likely to report unhappiness — a link that had been found in previous studies and that is consistent with popular perception about the link between your body's well-being and your mind's. Unhappiness was associated with smoking, lack of exercise and not living with a partner.
Here's what the happy group look like: They were older, had fewer educational qualifications, were doing strenuous exercise, were non-smokers, living with a partner and participating in religious or other group activities. They were also more likely to get a lot of sleep. The researchers reported that "the relation between happiness and the number of hours of sleep was J-shaped, with women reporting about 8 h sleep most likely to be generally happy."
But during 10 years of follow up, things didn't progress as might be expected.
The 4 percent or nearly 32,000 of the women who died were not unhappier than the rest. Neither were they more stressed or felt like they had less control over their lives.
In fact, after researchers adjusted for a number of factors — self-rated health, treatment for hypertension, diabetes, asthma, arthritis, depression, or anxiety, and several sociodemographic and lifestyle factors including smoking and body-mass index — women who were unhappy died at about the same rate as those who were happy. This trend held for all causes of death, including heart disease and cancer.
"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 of a million women," explained lead author Bette Liu, a researcher at the University of New South Wales, Australia.
Sir Richard Peto, a professor at the University of Oxford and a co-author, said that people who believe unhappiness and stress can directly cause disease are "simply confusing cause and effect."
"Of course people who are ill tend to be unhappier than those who are well, but [the study] shows that happiness and unhappiness do not themselves have any direct effect on death rates," he said in a statement.
Notice that in this graphic, which shows mortality (y-axis) against happiness and other measures of well-being (x-axis), all the lines are flat which shows no association between them.
In figure A, the reference group (RR=1.0) was women who reported being happy most of the time. In figure B, women who felt in control most of the time. In figure C, women who said they were relaxed most of the time. And in figure D, women who said they were rarely if never stressed.
The authors said the study is so large that it rules out unhappiness being a direct cause of any increase in overall mortality in women.
In a commentary piece accompanying the study, Philipe de Souto Barreto and Yves Rolland of the Institute of Ageing at the University Hospital of Toulouse in France are not as definitive. While they praised the robustness of the study's design and findings, they said more work needs to be done to tease out the impact of different kinds of happiness. Among them are hedonic happiness that defines well-being through experiences of pleasure vs. displeasure; subjective well-being, which encompasses moods and emotions as well as one's satisfaction with one's life; and positive psychological well-being, which uses standard scales of happiness that have partly to do with how much one feels to have self-control.
Liu and Peto acknowledged that one limitation of their study "there is no perfect or generally agreed way to measure happiness or related subjective indices of wellbeing" and that this limits their ability to compare across studies. For their work they used a single question about happiness with a four-point scale — but as any person can attest, happiness is infinitely more complex encompassing everything from family, work, health, religion and biology to other intangible factors.
So what does all this mean for men? The commentators wrote that the "happiness–mortality association seems to be, to some extent, sex-specific, with higher positive effects reported in men than in women." Translation: It's possible that a man's happiness level may influence his chances of dying. They say this may be because there appear to be big differences in how the genders interpret happiness.
De Souto Barreto and Rolland also raised the philosophical question of what defines a good life and how that relates to happiness, good health and longevity:
What defines a good life? If in answering this question you included happiness in your list, you are not alone. Indeed, the pursuit and enjoyment of happiness is a common goal and desire in life for most people. Adults of all ages, including those in old age, frequently report the experience of happiness as a determinant of a good life. Since both happiness and health are crucial aspects of quality of life, medical work about the potential positive effects of happiness on a person's health and longevity is a growing area that has received increasing attention in the past decade.