A new study concludes that “happiness and related measures of well-being do not appear to have any direct effect on mortality.”

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Go ahead and sulk. Unhappiness won’t kill you.

A study published Wednesday in The Lancet medical journal that followed 1 million middle-aged women in Britain for 10 years concluded that the widely held view that happiness enhances health and longevity is unfounded.

“Happiness and related measures of well-being do not appear to have any direct effect on mortality,” the researchers concluded.

“Good news for the grumpy” is one way to interpret the findings, said Sir Richard Peto, an author of the study and a professor of medical statistics and epidemiology at the University of Oxford. He and his fellow researchers decided to look into the subject because, he said, there is a widespread belief that stress and unhappiness cause disease.

Such beliefs can fuel a tendency to blame the sick for bringing ailments on themselves by being negative, and to warn the well to cheer up — or else.

“Believing things that aren’t true isn’t a good idea,” Peto said in an interview. “There are enough scare stories about health.”

The new study says earlier research confused cause and effect, suggesting that unhappiness made people ill when it is the other way around.

“It’s such a common belief that stress and unhappiness causes death and disease but it’s actually the other way around,” Peto said, adding: “People should focus on the real issues that shorten their lives, like smoking and obesity.”

The results come from the Million Women Study, which recruited women 50 to 69 from 1996 to 2001, and tracked them with questionnaires and official records of deaths and hospital admissions. The questionnaires asked how often the women felt happy, in control, relaxed and stressed, and instructed them to rate their health and list ailments such as high blood pressure, diabetes, asthma, arthritis and depression or anxiety.

Researchers included questions about happiness “because it’s something a lot of people were interested in,” Peto said.

When the answers were analyzed statistically, unhappiness and stress were not associated with an increased risk of death. It is not clear whether the findings apply to men. Indeed, in an accompanying commentary, French scientists suggested the results might not be the same in men, since “men and women probably define happiness differently.”

Peto said particularly important data came from 500,000 women who reported on their baseline surveys that they were in good health, with no history of heart disease, cancer, stroke or emphysema. A “substantial minority” of these healthy women said they were stressed or unhappy, he said, but over the next decade they were no more likely to die than were the women who were generally happy.

“This finding refutes the large effects of unhappiness and stress on mortality that others have claimed,” Peto said.

Unhappiness itself may not affect health directly, but it can do harm in other ways, by driving people to suicide, alcoholism or other dangerous behaviors, he warned.

This type of study, which depends on participants’ self-assessments, is not considered as reliable as a rigorously designed experiment in which subjects are picked at random and assigned to a treatment or control group. But the huge number of people in this study gives it power.

Still, some observers noted that measuring emotions is more nuanced and complex than simply declaring happiness or unhappiness.

“I would have liked to see more discussion of how people translate these complicated feelings into a self-report of happiness,” said Baruch Fischhoff, a psychologist at Carnegie Mellon University in Pittsburgh who studies decision-making, who was not involved in the study. “Think about everything that’s going on in your life

and tell me how happy you are. Happiness is a squishy measure.”

Results of earlier studies have been mixed, with some finding unhappiness causes illness and others showing no link, Fischhoff said.

“It looks to me like people have collected a lot of data without finding a clear signal,” he said. “So if there is some correlation out there, it’s not very big.”

An editorial accompanying the study in The Lancet noted that it had “the largest population so far in happiness studies,” and praised its statistical methods. But it also said more research was needed.

Peto said he doubted the new study would change many minds because beliefs about the perils of unhappiness are so ingrained. “People are still going to believe that stress causes heart attacks,” he said.

He also said the pursuit of happiness is worthwhile, even if it doesn’t extend life.

“Happiness is very nice,” said Peto, who was relieved to have finished the study after two decades. “I had some of it myself when I was young.”