A) Both multiple motor and one or more vocal tics have been present at some time during the illness, although not necessarily concurrently.
B) The tics occur many times a day (usually in bouts) nearly every day or intermittently throughout a period of more than 1 year, and during this period there was never a tic-free period of more than 3 consecutive months.
C) The onset is before age 18.
D) The disturbance is not due to the direct physiological effects of a substance (e.g. stimulants) or a general medical condition (e.g. Huntington's disease or post-viral encephalitis).
Source for Diagnostic Criteria: Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM-IV - Text Revision), published by the American Psychiatric Association, Washington D.C., 2000, the main diagnostic reference of Mental Health professionals in the United States of America and Canada
For a comprehensive description of Tourette Syndrome, please refer to the Forum Section titled The Tic Parade that contains numerous "Sticky" articles describing Tourette Sndrome
Related Forum article: What is Tourette Syndrome? Overviews & Handout Attachments