Mass hysteria mars the music.

On April 13, 1989, nearly 600 students from three junior and senior high schools tuned their instruments and cleared their voices for the 40th annual "Stairway of the Stars" concert in Santa Monica, Calif. No sooner had the assembly commenced than headaches, dizziness, weakness, abdominal pain and nausea spread among the student performers. About half the students -- but no one in the audience -- developed some combination of these symptoms; 16 girls in the soprano section of the chorus fainted. Officials quickly evacuated the auditorium and ambulances rushed 19 students to hospitals.

A survey of most of the students in the ill-fated orchestra, conducted three weeks after the episode and described in the September AMERICAN JOURNAL OF PSYCHIATRY, indicates they fell prey to "mass hysteria" -- not the sort exhibited by fans at a rock concert, but the sudden appearance in a group of temporary physical symptoms stemming from psychological causes. Researchers have previously noted several other outbreaks of mass hysteria among schoolchildren and adults. Numerous physical and emotional factors contribute to these occurrences, but in Santa Monica, social transmission played a key role, maintain psychiatrist Gary W. Small of the University of California, Los Angeles, and his colleagues. Illness most often struct those students who first observed a friend with symptoms, Small's team reports.

Of the 519 student performers who completed a questionnaire developed by the researchers, 247 reported a sudden illness at the concert. Chorus members from one school, particularly girls in the soprano section, experienced the highest rate of symptoms. Social transmission exerted the strongest effects in those youngsters, the researchers contend.

The survey also found that girls suffered a higher rate of illness than boys -- 51 percent compared with 41 percent. One-quarter of the symptomatic students had a chronic medical illness, most often asthma, that might have contributed to hysterical reactions, the researchers note.

A clear trigger for the brief incapacitation of the student orchestra evades investigators, "although the psychological stress of performance anxiety probably contributed to symptoms," Small's group concludes.