Studies suggest optimists live longer and enjoy better health than pessimists. The real mystery is why.

Among the findings of various studies:

Highy optimistic people have significantly lower death rates. Optimistic coronary bypass patients are half as likely as pessimists to require re-hospitalization.

People with positive emotions have lower blood pressure. The most pessimistic men are more than twice as likely to develop heart disease compared with the most optimistic.

But is it optimism that makes people healthy, or do healthy people understandably have a brighter outlook?

To get a better handle on things, scientists have adjusted their analyses in recent years to account for pre-existing medical conditions. Studies that made these adjustments found that existing illnesses don't negate the benefits of optimism, according to the May 2008 issue of Harvard Men’s Health Watch.

In one example of how humans keep their spirits up no matter what, researchers found older people suffering various illnesses still said they thought they were aging well. Another study found that the sick and disabled don't wallow in misery as is commonly believed.

Optimism, another study found, triggers activity in the same brain area that is known to malfunction among the depressed.

But why is optimism so beneficial?

Perhaps optimists enjoy better health and longer lives because they lead healthier lifestyles, build stronger social support networks, and get better medical care, the Health Watch article suggested.

Also, stress is known to kill, releasing hormones that cause deterioration of everything from your gums to your heart. Optimists might have lower levels of stress hormones.

Heredity could play a role, too. It is possible that genes predispose some people to optimism, and that the same genes affect health and longevity.

More study is needed, the Health Watch article contends, because it's likely that multiple mechanisms are involved.
多项研究表明，乐观者比悲观者更健康长寿。可其中的原因却一直是个谜。

各项研究结果显示：

十分乐观的人死亡率明显较低。在接受过心脏搭桥手术的病人中，乐观的病人再次入院的几率为悲观者的一半。

情绪乐观的人血压相对较低。最悲观的人患心脏病的几率为最乐观者的两倍多。

可问题在于，究竟是乐观让人健康还是健康的人更加乐观？

为了弄清这一问题，近年来科学家们调整了研究方法以解释现有疾病（对乐观情绪的影响）。据今年5月号的《哈佛男性健康观察》，经调整后的研究发现，现有的各种病症不会影响乐观情绪的积极作用。

其中一项研究对人们在任何情况下如何保持乐观情绪的问题进行了探究，研究人员发现一些受多种疾病困扰的老年人仍然觉得自己过得很好。另一项研究发现，病残人士并不像人们通常想像的那样郁郁寡欢。

还有研究发现，乐观能刺激抑郁人士脑部功能紊乱区域的活动。

但为什么乐观如此有效呢？

这篇在《哈佛男性健康观察》上发表的文章称，乐观者更健康长寿也许是因为他们的生活方式更健康，社会支持网络更有力，得到的医疗护理更好。

此外，大家都知道，压力具有很强的“杀伤力”，它能释放出让你从牙龈到心脏全身各个器官都衰竭的激素，而乐观者体内的压力激素水平则相对较低。

另外，遗传可能也是原因之一。可能基因会让一些人天生乐观，同时这些基因又会影响健康和寿命。

该文章指出，（完全解释这一现象）还需进行更多研究，因为这一现象可能涉及多种原理。