NEW YORK - Today's lesson: be happy, live longer. Now science seems to back the glass half-full approach.

A review of more than 160 studies on the connection between a positive state of mind and overall health and longevity has found "clear and compelling evidence" that happier people enjoy better health and longer lives.

In fact, evidence linking an upbeat outlook and enjoyment of life to better health and longer life was stronger even than that linking obesity to reduced longevity, according to the review published on Tuesday in the journal Applied Psychology: Health and Well-Being.

"I was almost shocked, and certainly surprised, to see the consistency of the data," said Ed Diener, a University of Illinois psychology professor emeritus who lead the review.

While Diener said a few studies he reviewed found the opposite, the "overwhelming majority ... support the conclusion that happiness is associated with health and longevity".

The review looked at eight different types of long-term studies and experimental trials of both human and animal populations.

For example, 5,000 university students studied for more than 40 years provided evidence that the most pessimistic students tended to die younger.

In the laboratory, positive moods were found to reduce stress-related hormones, increase immune function and help the heart recover following exertion.

Animals who lived in stressful conditions such as crowded cages had weaker immune systems and a higher susceptibility to heart disease, and died at a younger age than those in less crowded conditions.

Diener noted that while current health edicts focus on obesity, smoking, eating habits and exercise, "it may be time to add 'be happy and avoid chronic anger and depression' to the list".

Reuters