Happy people don't just enjoy life; they're likely to live longer too. A new study has found that those in better moods were 35 percent less likely to die in the next five years when taking their life situations into account.
The traditional way to measure a person's happiness is to ask them about it. But over the past few decades, psychologist and epidemiologist Andrew Steptoe of University College London said, scientists have realized that those measures aren't reliable.
It's not clear whether they "assess how they're actually feeling or how they remember feeling," he said. When answering, people are more likely to count their blessings and compare their experience with the lives of others.
The English Longitudinal Study of Aging tried to get more specific. It has followed more than 11,000 people age 50 and older since 2002.
In 2004, about 4700 of them collected saliva samples four times in one day and, at those same times, rated how happy, excited, content, worried, anxious, and fearful they felt.
The saliva samples still are awaiting analysis for stress hormones, but Steptoe and his UCL colleague Jane Wardle publish findings today on the links between mood and mortality in the Proceedings of the National Academy of Sciences.
Of the 924 people who reported the least positive feelings, 7.3 percent, or 67, died within five years. For people with the most positive feelings, the rate fell in half, to 3.6 percent, or 50 of 1,399 people.
Of course, it's possible that people who died sooner weren't as chipper because they were deathly ill or because of any number of other factors that affect both mortality and mood.
The researchers adjusted for age, sex, demographic factors such as wealth and education, signs of depression, health (including whether they'd been diagnosed with major diseases), and health behaviors such as smoking and physical activity.
Even with those adjustments, the risk of dying in the next five years was still 35 percent lower for the happiest people.
The research showed that good moods are correlated with long life, but it's not proof that happiness makes people live longer, Steptoe said.
Furthermore, "what we don't want to do, obviously, is make people feel guilty if they're not very positive people," Steptoe said.
"On the other hand, we know that people's life circumstances are also very relevant," he said, mean that it's important to make sure older people have adequate money, health care, and social support.
"I think this is pretty exciting and pretty powerful," said Laura Carstensen, a life span developmental psychologist at Stanford University, who was not involved in this study but published a smaller one this year with similar findings.
In her study, older people in the San Francisco Bay Area recorded their emotions five times a day for a week, then were followed for many years. For 111 people, she found that happier people lived longer than people who experienced more negative emotions.
Asking people to record their moods, she added, "really does give you something different than asking people to tell you about their lives."