- overactive behaviour/hyperactivity
- impulsive behaviour
- difficulty in paying attention
ADD refers to problems in concentration and attention; ADHD refers to ADD plus overactive and impulsive behaviours. The "official" UK term, Hyperkinetic Disorders, covers the aspects of hyperactivity and impulsive behaviours.
The causes of ADD/ADHD appear (currently) to be a mixture of genetic and environmental factors (possibly including diet). Children who have suffered brain injury or illness may also exhibit similar symptomatic behaviours.