Yet how to deal with hypochondria, a disorder that afflicts one of every 20 Americans who visit doctors, has been one of the most stubborn puzzles in medicine. Where the patient sees physical illness, the doctor sees a psychological problem, and frustration rules on both sides of the examining room.

Recently, however, there has been a break in the impasse. New treatment strategies are offering the first hope since the ancient Greeks recognized hypochondria 24 centuries ago. Cognitive therapy, researchers reported last week, helps hypochondriacal patients evaluate and change their distorted thoughts about illness. After six 90-minute therapy sessions, the study found, 55 percent of the 102 participants were better able to do errands, drive and engage in social activities. Antidepressant medications, other studies indicate, are also proving effective.