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Understanding the neurophysiology of feeling good is one aspect of happiness research; another is understanding how positive emotion affects the rest of the body. As with the brain studies, the term happiness is too broad for a rigorous approach, so researchers tend to focus on specific aspects. Harvard psychologist Kubzansky has chosen to study optimism. In a large study she tracked 1,300 men for 10 years and found that heart-disease rates among men who called themselves optimistic were half the rates for men who didn't.
"It was a much bigger effect than we expected," she says--as big as the difference between smokers and nonsmokers. "We also looked at pulmonary function, since poor pulmonary function is predictive of a whole range of bad outcomes, including premature mortality, cardiovascular disease and chronic obstructive pulmonary disease." Again, optimists did much better. "I'm an optimist," she says, "but I didn't expect results like this."
In a separate study, meanwhile, which has been accepted by the journal Health Psychology, Kubzansky, working with Duke psychologist and lead researcher Laura Richman, looked at hopefulness and curiosity--mental states that overlap with optimism in some ways. "We found them to be protective against hypertension, diabetes and upper-respiratory infection," she says. Such protective effects may explain the longevity advantage found in that Dutch study of the elderly--an advantage for happy optimists that persisted even when researchers corrected for diet, education and other factors.
Exactly how states of mind affect the body's biochemistry is still far from clear. "We can do some good speculation," says Kubzansky, "based on what we know about anxiety and depression, so there are a couple of places to look in terms of neuroendocrine function and immune inflammatory pathways." One clue: in addition to reporting a positive mood when their left prefrontal cortexes are active, subjects in Davidson's experiments have lower levels of cortisol, a hormone produced by the adrenal gland in response to stress--and cortisol is known to depress immune function. Optimists may simply feel less stress than pessimists and thereby avoid the noxious biochemical cascades that stress is known to trigger. Another likely factor: optimistic, happy types seem to take better care of themselves than sad sacks do. Numerous studies--as well as common sense--suggest that to be the case.
In a series of studies begun in 1998, psychologist Robert Emmons of the University of California at Davis has found further evidence that happy people are better at health maintenance. Emmons randomly assigned 1,000 adults to one of three groups. The first group kept daily journals of their moods and rated them on a scale of 1 to 6. The second group did that and listed the things that annoyed or hassled them throughout their day. The third group kept a journal but added an activity that has repeatedly been shown to improve one's sense of satisfaction with life: they were asked to write down every day all the things for which they were grateful.