The May issue of Harvard Men's Health Watch says many studies have reported optimism influences health. The findings include:

-- Optimistic coronary bypass patients were only half as likely as pessimists to require re-hospitalization.

-- Highly pessimistic men were three times more likely to develop hypertension.

-- People with positive emotions had lower blood pressures.

-- In one study, the most pessimistic men were more than twice as likely to develop heart disease compared with the most optimistic.

But people who are healthy are likely to have a brighter outlook than people who are ill, so perhaps optimism is actually the result of good health instead of the other way around.

To counter this argument, scientists have adjusted their analyses to account for pre-existing medical conditions and these studies found that existing illnesses did not tarnish the benefits of optimism, the newsletter says.

Optimists may enjoy better health and longer lives because they lead healthier lifestyles, build stronger social support networks and get better medical care, or optimism may have biological benefits, such as lower levels of stress hormones and less inflammation, the Health Watch says.