An epidemiological study of tics.

We devised a questionnaire for estimation of each tic, and used a two-step investigation procedure, first by a parent questionnaire with 1,218 responses and second by a confirmatory telephone interview for 197 positive responses. The average estimated values were 11.3% for boys and 5.2% for girls. The prevalences were--blinking: 4.2%, head-jerking: 1.6%, shrugging: 1.2%, mouth-twitching: 0.6%, face-distortion: 0.5%, mouth-opening: 0%, throat-clearing: 2.7%, sniffing: 0.6%, and vocalization: 0.2%. According to the criteria in DSM-III-R, 5.1% of 1,218 had TTD, 2.2% had CMVTD, and 0.5% had Tourette disorder.