By understanding the science of happiness and applying the findings, more people can enjoy greater life satisfaction. But, finding happiness is not just about feeling good or feeling positive emotions for the sake of pleasure.

Happiness and other positive emotions may have a powerful influence on our health. They can make your immune system function better, provide a protective effect against some diseases and even help you live longer.

Happiness and related mental states, such as, hopefulness, optimism and contentment appear to decrease the risk or limit the severity of diabetes, hypertension, cardiovascular and pulmonary diseases as well as colds and upper-respiratory infections.

People who rate higher for happiness on psychological tests develop about 50% more antibodies than average in response to flu vaccines. A Dutch study of elderly patients showed that those with upbeat mental states reduced the risk of death by 50% over the nine-year duration of the study.

In contrast, clinical depression  —  which is the extreme opposite of happiness  —  has been shown to worsen heart disease, diabetes and other illnesses.

A 10-year study on optimism tracking 1300 men was done by Kubzansky, a Harvard psychologist. This study showed that rates for heart disease among men who called themselves optimistic were half the rates for men who didn't consider themselves optimists.

The health effect associated with optimism was much bigger than was expected  —  this was as big as the difference between smokers and nonsmokers.

The effect of optimism on pulmonary function was also studied. Poor pulmonary function can lead to cardiovascular disease, chronic obstructive pulmonary disease and premature mortality. In this study, optimists did much better than pessimists.

In another study looking at hopefulness and curiosity  —  mental states that are associated with optimism  —  Kubzansky was working with Laura Richman, a Duke psychologist and lead researcher. They found that hopefulness and curiosity were protective against hypertension, diabetes and upper-respiratory infection.

How our minds affect our body’s biochemical processes is not clear.

There are some clues provided by the happiness studies. When test subjects reported their positive mood in Davidson’s experiments  —  the left prefrontal cortex of their brains were activated  —  and they were also found to have lower levels of cortisol, a hormone produced by the adrenal gland in response to stress. Cortisol is known to depress immune function. These studies suggest that optimists may have less response to stress compared to pessimists thereby avoiding the harmful effects triggered by stress. Alternatively, optimists may take better care of themselves compared to pessimists.

By having a greater understanding of happiness, we can create new treatments and improve current treatments to combat clinical depression  —  the findings may also be useful in promoting or enhancing happiness. In turn, greater happiness may lead to people having better health and living longer.