[Hyperactivity in children: a valid diagnosis?].

Research has documented differences between hyperactive and normal children. However, to be valid, a diagnostic entity must differ in etiology, course, characteristics, or treatment response from other behavior problems as well as from normality. In order to demonstrate the validity of this syndrome, the research has followed three lines: the search for a biological marker, the study of symptoms and the evaluation of the suspected cognitives deficits. No final answers have been obtained yet but understanding of this clinical entity is still progressing.