The relationship between motor response inhibition, tic severity and ADHD in patients with Gilles de la Tourette Syndrome

Abstract

Background: Gilles de la Tourette Syndrome (GTS) is a neuropsychological developmental disorder characterized by tics. Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common comorbidities of GTS. There are suggestions that GTS and ADHD are etiologically related in the area of inhibition failure. Method: To study whether serial response time, as measured by the serial response time task is associated with tic severity, and severity of co-morbid ADHD, and might serve as predictor of outcome, in total 28 GTS patients and 30 healthy control participants participated in the study. The GTS patients all finished the YGTSS, Y-BOCS, CAARS and the SRT and the control group finished the ticscreener, CAARS and the SRT. In the analyses, education level and gender were included as co-variates, since there were significant between-group differences on these measures. Results: GTS patients with 1) higher ADHD severity and with 2) higher YGTSS tic severity showed at trend level- longer inhibition times compared to 1) GTS patients with low tic severity or 2) GTS + low ADHD scores, and controls. Other comparisons revealed no between-group differences. Gender en education level were significant predictors of response time, and education level was a predictor of the amount of errors on the SRT. Outcomes on the SRT neither predicted current tic severity nor change in tic severity over time in GTS patients. Conclusions: in this study, longer response time was –at trend level – associated with current tic severity and with co-morbid ADHD, but does not seem to predict tic severity change. These findings need to be replicated in future studies, using larger sample size, wider range in age and a larger variation in tic severity