Involuntary motor movements [tics], such as head twitching, or vocalizations, such as grunts, that often occur in rapid succession, come on suddenly, and happen in idiosyncratic or stereotyped ways. Vocal tics often include the involuntary repetition of obscenities.
Of all children, up to 20% show some tics during their growing years, and I to 10 children out of every 1,000 have Tourette's Disorder. Usually develops before the age of 14. High Comorbidity between tics and ADHD, as well as Obsessive-compulsive disorder.
There are likely multiple vulnerability genes that of influence the form and severity of tics.
David H. Barlow, BOSTON UNIVERSITY
V. Mark Durand, UNIVERSITY OF SOUTH FLORIDA- ST. PETERSBERG
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