Inhibition is impaired in children with obsessive-compulsive symptoms but not in those with tics

BACKGROUND: Impaired inhibitory control is thought to be a core deficit in psychiatric disorders where patients exhibit problems with controlling urges. These problems include the urge to perform movements typical of Tourette syndrome and the urge to execute compulsive actions typical of obsessive-compulsive disorder. However, the picture emerging from studies that address this issue is controversial. Furthermore, most studies have only focused on reactive control (the ability of subjects to react to a stop signal), but not on proactive control (the ability of patients to shape their response strategies in anticipation of known task demands). OBJECTIVES: We assessed reactive and proactive inhibitory control in drug naïve children/adolescents affected by Tourette syndrome, obsessive-compulsive disorder, and in those in which the 2 disorders co-occur. METHODS: Reaching version of the stop signal task and of a simple reaction time task were given to 37 unmedicated patients (mean age ± SD, 11.0 ± 2.3) and to 37 healthy age- and gender-matched controls (mean age ± SD, 10.8 ± 1.6). RESULTS: Both reactive and proactive inhibition scaled with the severity of obsessive-compulsive symptoms, but not with those of tic symptoms (ie, inhibitory control in uncomplicated Tourette patients was comparable with that of healthy controls). CONCLUSIONS: We suggest that the cognitive mechanisms underlying tics and compulsions controls are likely to be different. Possibly the preserved ability to suppress actions in uncomplicated Tourette patients allows them to experience a greater feeling of self-control, and this fact might play a key role in evolution of the disorder beyond adolescence.