Research into the physiology of psychological stress - how it changes the operation of metabolism and seems to accelerate some measures of aging - opens the door to asking whether other states of mind or character traits can affect human health and longevity in measurable ways. The difficulty of establishing measures of mental states makes this an unpopular topic for discussion in some reaches of the scientific community, and I'd be the first to say that a great deal of what passes for soft science these days is a waste of time and money. But there are physiological links between metabolism, aging, and the physical structure that forms the mind, so in the long run there should be some way to measure, assess, and correlate these links.
One thorny problem in this endeavor is that people don't conveniently live in laboratory tanks, and the choices they make in lifestyle and use of medical services throughout their free-range lives have a large impact on health and longevity. It's not hard to find studies that show strong correlations for longevity that might be traced back to people who are more conscientious in taking care of their health, or greater wealth and access to medicine, or greater access to knowledge that in turn leads to better healthcare and bodily maintenance. And so forth.
That all said, here's an open access paper that looks at a narrow range of character traits and their effects on survival rates of older people:
The just world hypothesis and how it may relate to health and longevity is easily stated. Individuals have a strong need to believe that they live in a world where people generally get what they deserve. The belief that the world is just enables the individual to confront his/her physical and social environment as though they were stable and orderly. Without such a belief, it would be difficult for the individual to commit himself/herself to the pursuit of long-range goals or even to the socially regulated behavior of day-to-day life.
Since the belief that the world is just serves such an important adaptive function for the individual, people are very reluctant to give up this belief, and they can be greatly troubled if they encounter evidence that suggests that the world is not really just or orderly after all. According to Lerner and Miller's just-world theory, people who believe that the world treats them fairly may plan confidently for their future, expecting their lives to be orderly, meaningful, and controllable, foreseeing a positive future or viewing one's living situation as justly deserved and hence fair. In turn, this expectation promotes mental health, meaning that the belief in a just world (BJW) can be seen as a "positive illusion". Indeed research links BJW to many indices of subjective well being including a greater purpose in life and commitment to planned healthy survival. There is empirical evidence showing that individuals who strongly believe in a just world have been seen to experience less stress and more positive affect than individuals with a weaker BJW.
The authors pull in data gathered from hundreds of study participants across the better part of a decade to support their hypothesis for this trait and a few others - including levels of distrust and the degree to which individuals see an open and expansive future ahead of them. The authors see definitive correlations between these comparatively narrow traits and mortality rates, and we might make guesses as to the mechanisms by which these correlations are established. Mechanisms similar to those linking stress with our biology, or more to do with the practice of good health over the years? The paper makes for interesting reading no matter your thoughts on whether this sort of research has any real merit.