In 1902, a paper published in The Lancet pointed to the fact that ‘abnormal physical conditions in children’ could be caused by diseases of the central nervous system (CNS). This conclusion was based on observations of children developing hyperactive, antisocial behaviour after encephalitis (Still, 1902). Kahn and Cohen further discussed the clinical picture in 1934, introducing the concept ‘organic driveness’ (Kahn & Cohen, 1934). Bradley (1937) reported clinical efficacy of CNS stimulants in hyperactive children a few years later.

The concept of minimal brain dysfunction (MBD) was used for many years to describe children with hyperactivity and attention problems. However, this concept was used differently both between and within countries, thus making comparison of research reports problematic and clinical evaluations different. Accordingly, the MBD concept has been abandoned in clinical practice and research, whereas Attention Deficit Hyperactivity Disorder (ADHD) has become the internationally accepted term and diagnosis for the group of children described as MBD or hyperactive in older publications (APA, 1994).

Hyperactivity is regarded as a predominant symptom in ADHD children, but the relative importance of this symptom has been discussed extensively over the years. In The Diagnostic and Statistical Manual-III of The American Psychiatric Association (DSM-III), the syndrome was subdivided into attention deficit disorder with or without hyperactivity. The DSM-III revision broke this down into ADHD only, thus demanding that hyperactivity should be present in order to diagnose ADHD. In the DSM-IV (APA, 1994), the sub-division reappeared (predominantly inattentive, predominantly hyperactive or both).