Reexamining Tic persistence and Tic-associated impairment in Tourette's Disorder: findings from a naturalistic follow-up study.
The objective of this study was to assess tic persistence and tic-associated impairment in referred youth with Tourette's Disorder (TD). Subjects were 50 youth (ages 6-17 years) who met DSM-IV diagnostic criteria for TD, were referred to a specialized TD program, and were evaluated by clinical and structured diagnostic interview. Tic severity and impairment was measured using the Yale Global Tic Severity Scale. The total tic score at or above minimal range defined tic persistence, and a TD impairment score at or above moderate range defined tic-associated impairment. Results were assessed during administration of the Kiddie-Schedule for Affective Disorders and Schizophrenia for School-Age Children-Epidemiological Version. Mean age of onset of TD was 5.1 +/- 2.3 years, and mean illness duration was 5.6 +/- 3.2 years. At baseline, 88% of subjects met threshold criteria for at least mild tics, but only 30% met criteria for tic-associated impairment. At 2-year follow-up, 82% of these subjects met criteria for tic persistence (NS change from baseline), but only 14% met criteria for TD-associated impairment (p < .04 change from baseline). Although tics followed a persistent course in the majority of youth with TD, they were infrequently associated with impairment. There was a significant reduction in the proportion of youth with TD impairment from baseline to follow-up. These results support the view that TD is a persistent disorder, but suggest a dissociation between tic persistence and tic-associated dysfunction.