Autism spectrum disorder and ADHD often overlap. Attention Deficit Hyperactivity Disorder is a common condition in children with mental retardation. Many autistic children also have symptoms of ADHD. Children with ADHD often have difficulty paying attention to the same thing for too long, and they may get distracted easily. Autistic children may have a limited scope of interest. They may seem to obsess over things that they enjoy and have difficulty focusing on things that they have no interest in.