ADHD is an impairment of either activity or attention control or both. The problem usually presents as a child who is always on the go, does not settle to anything, has poor concentration, poor ability to organise activities or to engage in tedious activities or tasks requiring sustained mental effort, or who cannot stay still and will not wait for others.
Some children (with attention deficit otherwise known AD) do not present the full condition, but only the component of inattentiveness. They are forgetful and disorganised and do not focus their concentration well, but their activity levels are normal or even underactive.
Hyperkinetic disorder is a severe subtype of ADHD in which all the problems are present in several situations (both at home and school).
In addition, some affected children show underachievement at school, motor clumsiness, poor sleep, social interaction difficulties, autistic-type features (see entry Autism Spectrum disorders, including Asperger syndrome), speech and language difficulties (see entry Speech and Language Impairment), discipline problems, temper tantrums, unpopularity, or proneness to have accidents. All these, however, can have other causes too. The IQ of an individual with ADHD can be high, normal, low normal or in the learning disability (see entry Learning Disability) range.