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Children with comorbid attention-deficit-hyperactivity disorder and tic disorder: evidence for additive inhibitory
G H Moll1, H Heinrich, G E Trott
1Child and Adolescent Psychiatry Department, University of Göttingen, Germany.
Insights
Children with ADHD and tic disorders show additive motor system excitability deficits. Neurophysiological findings reveal reduced intracortical inhibition and shortened cortical silent periods in comorbid cases.
Area of Science:
- Neuroscience
- Pediatric Neurology
- Clinical Neurophysiology
Background:
- Attention-deficit-hyperactivity disorder (ADHD) and tic disorder (TD) are common childhood conditions.
- Previous research indicated motor system inhibitory deficits in children with ADHD or TD individually.
- These deficits, specifically reduced intracortical inhibition (ADHD) and shortened cortical silent period (TD), correlate with hyperactivity and tics.
Purpose of the Study:
- To investigate the neurophysiological underpinnings of comorbidity in children with both ADHD and TD.
- To assess motor system excitability in children experiencing combined ADHD and TD.
- To determine if additive effects exist at the motor system level in comorbid cases.
Main Methods:
- Utilized transcranial magnetic stimulation (TMS) to measure motor system excitability.
- Assessed intracortical inhibition and cortical silent periods in the motor system.
- Included groups of children with ADHD, TD, and combined ADHD and TD.
Main Results:
- Children with combined ADHD and TD exhibited reduced intracortical inhibition.
- These comorbid children also showed a shortened cortical silent period.
- Findings suggest additive neurophysiological effects on motor system excitability.
Conclusions:
- The study provides novel neurophysiological evidence for additive effects in children with comorbid ADHD and TD.
- Deficient inhibitory mechanisms in the motor system are present in both conditions and are compounded when they co-occur.
- These findings enhance understanding of the neurobiology of combined ADHD and TD.
Abstract:
For children with attention-deficit-hyperactivity disorder (ADHD) or tic disorder (TD), we recently reported deficient inhibitory mechanisms within the motor system by using transcranial magnetic stimulation. These deficits--stated as reduced intracortical inhibition in ADHD and shortened cortical silent period in TD--could be seen as neurophysiological correlates of motor hyperactivity and tics, respectively. To investigate neurophysiological aspects of comorbidity, we measured motor system excitability for the first time also in children with combined ADHD and TD. The findings of a reduced intracortical inhibition as well as a shortened cortical silent period in these comorbid children provide evidence for additive effects at the level of motor system excitability.