An experimental evaluation of tic suppression and the tic rebound effect.

Tourette's syndrome (TS) is a neurobiological disorder consisting of motor and vocal tics that are thought to be temporarily suppressible. Many professionals, however, believe that a paradoxical increase in tic frequency (above baseline levels) occurs when efforts to suppress have ceased (i.e., a rebound effect). To date, little research has investigated tic suppression or its effects. This study examined tic frequency during baseline, suppression, and post-suppression conditions using an experimental preparation reported to reliably produce tic suppression in children. Six children with TS and one with chronic tic disorder (CTD) were recorded during baseline and repeated suppression and post-suppression conditions. Tic frequency was significantly lower during suppression as compared to baseline. Although tic frequency during post-suppression was higher than during suppression, it was lower than baseline levels, arguing against a "rebound" effect of tic suppression. Exploratory analyses revealed that scores on the attention problems subscale of the Child Behavior Checklist significantly predicted tic suppressibility. The relationships between age, tic severity, and tic suppressibility were also explored.