Background: Autism Spectrum Disorders (ASD), Attention Deficit Hyperactivity Disorder (ADHD) and Tourette Syndrome (TS) are neurodevelopmental disorders with strikingly different clinical manifestations and presentations. However, despite such disparate clinical presentations, they frequently show co-morbidity suggesting potentially similar etiological mechanisms. Autonomic dysregulation has been reported independently in each of these conditions, though comparisons of the nature of this dysregulation across disorders are rare