“We reviewed eight different types of studies,” Diener said. “And the general conclusion from each type of study is that your subjective well-being – that is, feeling positive about your life, not stressed out, not depressed – contributes to both longevity and better health among healthy populations.”
A study that followed nearly 5,000 university students for more than 40 years, for example, found that those who were most pessimistic as students tended to die younger than their peers. An even longer-term study that followed 180 Catholic nuns from early adulthood to old age found that those who wrote positive autobiographies in their early 20s tended to outlive those who wrote more negative accounts of their young lives.
Of course there's the question of the direction of cause and effect. People with better health will be happier. Ditto smart people who see their way to success. A healthier and more capable body and mind has greater odds of having what it takes to go the distance.
There were a few exceptions, but most of the long-term studies the researchers reviewed found that anxiety, depression, a lack of enjoyment of daily activities and pessimism all are associated with higher rates of disease and a shorter lifespan.
Of course you might be thinking defeatist thoughts at this point: "My pessimistic outlook means I shouldn't even try to exercise and eat better since I'll die young regardless".
A new study led by a Michigan State University business scholar suggests customer-service workers who fake smile throughout the day worsen their mood and withdraw from work, affecting productivity. But workers who smile as a result of cultivating positive thoughts – such as a tropical vacation or a child’s recital – improve their mood and withdraw less.
So think positive thoughts about a tropical island or a road trip or a night on the town.