Attention deficit hyperactivity disorder (ADHD) symptoms, comorbid psychopathology, behaviour problems and gastrointestinal symptoms in children and adolescents with autism spectrum disorder.

The study aims to investigate attention deficit hyperactivity disorder (ADHD) symptoms, gastrointestinal (GI) symptoms, comorbid psychopathology and behaviour problems in children and adolescents with autism spectrum disorder (ASD). Parents of 147 children and adolescents with ASD aged 6-18 years completed the Conners 3 Parent-Short Form, Gastrointestinal Symptom Inventory, Behavior Problems Inventory-Short Form and Autism Spectrum Disorder-Comorbid for Children. Fifty-six per cent of children and adolescents had a comorbid diagnosis of ADHD, yet over 70% presented with clinically significant ADHD symptoms. Forty per cent of participants received a diagnosis of ADHD before ASD and 25.6% received a diagnosis of ASD first. Relationships were found between ADHD symptoms and comorbid psychopathology, GI symptoms, and behaviour problems. The outcomes suggest that ADHD is being underestimated as a comorbid disorder of ASD. This may have implications on treatment and interventions for children and adolescents who have a diagnosis of both ASD and ADHD.