A new study has come to a rather surprising conclusion: Happiness and unhappiness do not lead to a longer life or quicker death. Instead, our self-reported levels of happiness may be a byproduct of our overall health status.
The finding upends conventional wisdom on the link between happiness and health – and evidence used to make the claim is impressive. Researchers used data collected from one million women in Britain who were involved in the aptly named Million Women Study from 1996 to 2003. They were asked to rank their health and happiness throughout the study period and researchers recorded information from them about physical activity, smoking, education, social life and living situation. In 2012, the researchers checked in to see how many women had died and from what causes.
The authors of the study, published on Wednesday in The Lancet, noted that unhappiness was strongly linked to poor health and increased risk of death. But after adjusting for poor health and the lifestyle factors that could lead to illness, such as smoking and inactivity, the researchers found virtually no difference in the mortality rate between happy and unhappy individuals.
The researchers concluded that other studies linking happiness to a longer life and unhappiness to a hastened death were simply confusing cause and effect. Or, put another way, they concluded that suffering from disease or other illnesses causes people to be unhappy and it also causes them to die earlier. Simply being unhappy on its own does not.
"I think it shows clearly that happiness doesn't make you live longer and that studies have suggested that this might have been the case haven't properly accounted for ill health," lead author Bette Liu, an epidemiologist at Australia's University of New South Wales, said in an e-mail.
But, like most things, it turns out the answers are not that simple.
A complicated question of health and happiness
The study authors reached their conclusions by essentially excluding people who were unhappy and in poor health. They explain that unhappy people who suffer from illness, smoke or who are inactive, for instance, feel unhappy because of their health.
But excluding those people is a mistake, argues Timothy Lau, clinical lead of the geriatric program at the Royal Ottawa Mental Health Centre. The people who rated themselves as unhappy during the study who suffered poor health could have been unhappy long before those physical ailments began, he explained. In other words, people who are unhappy for a long time may develop health problems. This study didn't properly address that issue, he said.
He and Chris Barrington-Leigh, an assistant professor at McGill University's Institute for Health and Social Policy, point to another study for better clues about the interplay between health and happiness: the nun study. That study, which began in 1986, followed hundreds of nuns to track their health and longevity. Researchers found that nuns whose happiness was considered high when they entered the convent lived, on average, seven years longer than nuns rated as unhappy.
Barrington-Leigh said the study is powerful because all of the nuns were young and relatively healthy when they entered the convent, yet their happiness level at that young age corresponded to an earlier or later death.
Happy or unhappy, what is the question?
At the end of the day, what is the point of living a long life if a person is unhappy?
The better issue to focus on, both Lau and Barrington-Leigh say, is how to improve a person's overall well-being.
This is a question a growing number of governments and international organizations are interested in answering as a way of bridging inequality gaps and improving the health status of the population, according to Barrington-Leigh.
"What we care about here is the quality of people's lives, not just how long we keep them going," he said.
On that point, Liu, author of the study reported in The Lancet, agreed, noting that her results show the need to focus on things proven to improve overall health, such as reducing smoking rates.
"We know this prevents disease and improves people's health and in that way will likely increase people's happiness," she wrote.