The puzzling question of inhibitory control in Tourette syndrome: A meta-analysis

- Impulse control disorders are somewhat frequent in Tourette syndrome (TS) patients.
- Inhibitory control is impaired in TS patients, even when they do not have any comorbid disorder.
- Comorbid ADHD has a potentiating effect on the inhibitory deficits of TS patients.
- TS patients have impairments in verbal inhibition and Stroop interference, but show intact Go/No-Go performance.

Tourette syndrome (TS) is a neuropsychiatric disorder involving motor and phonic tics. Inhibitory control is a key issue in TS, and many disruptive or impulsive behaviors might arise from inhibitory deficits. However, conflicting findings regarding TS patients' inhibitory performance in neuropsychological tasks have been reported throughout the literature. Therefore, this meta-analysis aimed to evaluate inhibitory control through neuropsychological tasks, and to analyze the factors modulating inhibitory deficits.To this end, a literature search was performed through MEDLINE and PsycINFO, to retrieve studies including neuropsychological tasks that assessed inhibitory control in TS patients. Of the 4020 studies identified, 61 were included in the meta-analysis, for a total of 1717 TS patients.Our analyses revealed a small to medium effect in favor of inhibitory deficits in TS patients. This effect was larger in TS + ADHD patients, but pure TS patients also showed some inhibitory deficits. Therefore, deficits in inhibitory control seem to be an inherent component of TS, and are exacerbated when ADHD is concomitant.