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As devastating as illness can be, it doesn't have the power to permanently steal every ounce of happiness. But healthy people sometimes overlook happiness, while their ailing peers are more attuned to it.

That's what Jason Riis and colleagues found in comparing 49 kidney dialysis patients with 49 healthy people. Riis, now research assistant at Princeton University (search), was a University of Michigan (search) graduate student when he worked on the study.

The kidney patients were just about as happy as healthy participants — and they were more aware of their own happiness, too.

The Happiness Experiment

The dialysis patients had end-stage renal disease, a chronic condition in which the kidneys don't work properly.

Most patients need dialysis sessions three times per week. Each session lasts three hours. Patients can often participate in normal activities, but they usually have a strict diet and can feel tired if they miss treatment for several days, say the researchers.

Each patient had been on dialysis for at least three months. They were compared with healthy people of the same age and gender. All were given personal digital assistants (PDAs) such as Palm Pilots (search) to carry for seven days.

The PDAs beeped at random times throughout the day, quizzing participants about their feelings at that moment. The goal was to create a series of emotional snapshots.

Participants also imagined themselves in someone else's shoes. Healthy subjects predicted how they would feel if they needed dialysis. Kidney patients had the reverse question, pondering how freedom from dialysis and kidney problems would affect their mood.

Estimating Happiness

The kidney patients weren't any unhappier than the healthy people.

"They do not appear to be much, if at all, less happy than people who do not suffer from kidney disease or from any other serious health condition," write the researchers in The Journal of Experimental Psychology.

What's more, healthy people slightly understated their moods, shortchanging their happiness.

The dialysis patients didn't do that. Their happiness estimates were right on track. Apparently, they had largely adapted to their condition, say the researchers.

The kidney patients weren't deluded. They knew their condition was much worse than that of healthy people. But they didn't seem to be exaggerating their moods, say Riis and colleagues.

Grass Greener ... or Not?

The dialysis patients seemed unaware of how well they had adjusted. "They believe they would be happier if they had never been sick, yet they appear to be incorrect in this belief, as they are already about as happy as healthy people," say the researchers.

Healthy people also misjudged the emotional impact of illness. They imagined that dialysis would wreck their moods much more than it did for the real-life kidney patients.

"Healthy people expect dialysis to lead to a much more miserable life than it, in fact, does," say the researchers. "But this misperception will be a difficult one to correct. Even dialysis patients, who have themselves experienced adaptation, seem not to appreciate the extent of their own adaptation."

Misguided Consequences

The study isn't saying that a chronic condition is a light burden. Instead, it shows the potential to adapt emotionally, given time and experience.

Healthy people might want to keep that in mind, should they ever need to make important medical decisions for themselves, say the researchers.

"For most of us, it would take a lot more than we think to make us permanently miserable," they write.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Riis, J. Journal of Experimental Psychology. News release, University of Michigan.