Autism and attention-deficit/hyperactivity disorder traits as predictors of tic phenomenology in children and adolescents.

The co-existence of autism and attention deficit/hyperactivity disorder in tic disorders is a key factor influencing clinical decision-making. Given the shared clinical features and a potentially overlapping aetiology, the need to identify specific tic characteristics associated with these conditions remains. The current study subsequently sought to identify tic phenomenology uniquely predicted by autism and attention deficit/hyperactivity disorder traits in children and adolescents. Data from 473 5-16-year-olds from the 2004 British Child and Adolescent Mental Health Survey with motor and/or vocal tics were used. Regression analyses were conducted to determine the effect of autism and attention deficit/hyperactivity disorder traits on: (i) the presence of motor and/or vocal tics, (ii) tic onset age, (iii) nocturnal tic expression, (iv) self-regulatory control over tic expression, (v) tic frequency during restful/low arousal state, and (vi) rebound tic activity post-suppression, before and after adjustment for confounders. Autism is associated with earlier onset of tics by approximately 2.43 years. Attention deficit/hyperactivity disorder traits are associated with a 2.64x odds of experiencing worsening tics following periods of suppression. Neither autism or attention deficit/hyperactivity disorder traits were specifically associated with motor and/or vocal tics, self-regulatory control over tic expression, nocturnal tic expression, or tic frequency during restful/low arousal states. Comorbid neurodevelopmental traits not only co-occur with tic disorders but actively shape their clinical expression and trajectory. Clinically, earlier support for autistic children with tics may facilitate a timely intervention. Intervention plans for individuals with attention deficit/hyperactivity disorder traits should consider heightened vulnerability to tic rebound post-suppression.