Despite what able-bodied healthy people might think, people with severe illnesses and disabilities don't wallow in misery and self-pity all the time.

In fact, a new study finds, such patients on the whole may be just as happy as those without major medical conditions.

The finding adds to the growing body of evidence that ill and disabled people adapt to their condition and show a resilience of spirit that many healthy people can't imagine. It's published in the new issue of the Journal of Experimental Psychology: General by a team led by University of Michigan Health System researchers.

The researchers made their surprising finding by having 49 pairs of dialysis patients and healthy people report their mood every few hours for a week, using a handheld personal digital assistant (PDA) such as a Palm. The patients had all been in dialysis for at least three months, visiting a hemodialysis center three or more times a week for hours at a time to have their blood cleaned because their kidneys had failed.

Lead author Jason Riis, a former U-M graduate student now at Princeton University, programmed the PDAs to beep randomly during each two-hour period of an entire week, and prompt participants to report their mood at those random moments by completing a quick series of ratings.

"The big advantage of using PDAs is that you can get representative snapshots of a person's experience, rather than just relying on their overall impressions of their lives," says Riis, adding that several studies have shown such overall impressions to be biased in a variety of ways. "Our snapshots revealed that the patients were in good moods the vast majority of the time, and that their moods were not substantially worse than those of the healthy people."

"This is further evidence that people adapt emotionally to serious adversity, such as end-stage kidney failure," says senior author Peter Ubel, M.D., a U-M professor of internal medicine and psychology, and a staff physician at the VA Ann Arbor Healthcare System. "People who haven't experienced such adversity assume that it would destroy their happiness when in truth it probably would not."

In fact, the researchers found that the healthy participants grossly underestimated the extent to which patients can adapt to dialysis. When asked to imagine that they were themselves dialysis patients, and to estimate the percentage of time that they would experience various positive and negative mood levels, the healthy participants assumed that they would be miserable.

They thought they would experience negative moods most of the time, and on average have moods that were much lower than what the real patients actually experienced.

Interestingly, the patients themselves seemed to underestimate their own adaptation. When asked to imagine the moods they would experience if they had never experienced kidney failure, the patients estimated that they would experience much better moods than those actually experienced by the healthy study participants.

The study involved healthy participants whose age, gender, race and education were similar to the patients. In all, 60 participants were white, 36 were black, and one was Hispanic.

The study does more than just give the first-ever glimpse into the hour-by-hour happiness of seriously ill and healthy people, Ubel notes. It may also help influence policy-level and personal decisions about treatments for serious illnesses.

For instance, someone who has been healthy but who is facing a decision about whether or not to have a colostomy, an amputation or a risky operation might worry that the procedure would make his or her life miserable. But in fact, it probably wouldn't.

That's not to say that a major health catastrophe doesn't change a person's life, nor that going on dialysis, losing a limb or using a wheelchair doesn't change a person's experience of life, Ubel says. It's also not to say that such a major change wouldn't come without periods of frustration and difficulty, risk of depression or effects on a person's social or economic situation.

But the evidence from the new study, and from studies before it, suggests that people who have gone through such changes tend to adapt their emotional response to their new life. In the words of some of Ubel's patients, "What use is there in complaining?"

"People are more resilient than they think they can be, and can get through things that they probably would have never thought they could," says Ubel. "The fact that people seem to be so poor at estimating the effect of illness on mood calls into question some of the ways we use such quality-of-life estimates in policy making and research."

In addition to recording the "snapshots" of mood, and the predictions of what life would be like in the other group's shoes, the researchers also had the patients and healthy controls recall the moods they had experienced during the week they had carried the PDA. While healthy people slightly underestimated their previous week's average mood, the patients were quite accurate in recalling theirs. The researchers speculate that the patients' recall accuracy may be involved in the adaptation process, but say that further research is needed on this area.

The researchers now hope to expand the use of moment-based well-being measures to assess people with a range of health conditions, including those associated with pain and mental illness, where the adaptation story many be quite different.

There was no difference between the 49 patients and the 49 healthy participants in the average hour-by-hour rating of their overall mood, which on the whole tended to be on the positive side. There was also no difference between the two groups in the average measures of specific momentary moods, such as "depressed," "pleased" or "worried/anxious." Even questions about pain, tiredness and overall life satisfaction showed no significant differences.