Inhibitory control in youth with Tourette's Disorder, attention-deficit/hyperactivity disorder and their combination and predictors of objective tic suppressibility

The present study investigated inhibitory control deficits in Tourette's Disorder (TD)-only, Attention Deficit/Hyperactivity Disorder (ADHD)-only, and TD+ADHD and explored the degree to which measures of inhibitory control, and tic and ADHD severity predicted objective tic suppressibility. Participants were youth ages 9 to 14 (M = 11.15) with TD-only (n = 24), TD+ADHD (n = 19), ADHD-only (n = 139), and typically-developing controls (n = 59) drawn from a larger study. Groups were compared on computer-based and paper and pencil neurocognitive inhibitory control tasks. Among youth with TD, neurocognitive measures of inhibitory control, subjective tic-suppressibility (Premonitory Urge for Tics Scale, item 10), and ADHD symptom severity were evaluated as predictors of objective tic suppressibility (i.e., laboratory-based tic suppression task), controlling for total tic severity. There were significant group differences on Color-Word inhibition/switching performance, though post-hoc comparisons yielded no significant pairwise group contrasts. Subjective tic suppressibility was the only significant predictor of objective tic suppressibility. The evident intact neurocognitive inhibitory control among youth with TD suggests that individuals with TD may use compensatory neural mechanisms to support typical speed and accuracy of response. The role of cognitive flexibility in mechanisms of tic suppression should also be further explored.