 Though the American Psychiatric Association's criteria for Attention Deficit Hyperactivity Hisorder (ADHD), and the World Health Organization's criteria for hyperkinetic disorder each list a very similar set of 18 symptoms, the differing rules governing diagnosis mean that hyperkinetic disorder features greater impairment and more impulse-control difficulties than typical ADHD, and it most resembles a severe case of ADHD combined type.Unlike ADHD, a diagnosis of hyperkinetic disorder requires that the clinician directly observes the symptoms (rather than relying only on parent and teacher reports); that onset must be by age 6 not 7; and that at least six inattention, three hyperactivity and one impulsivity symptom be present in two or more settings.While ADHD may exist comorbid with (in the presence of) mania or a depressive or anxiety disorder, the presence of one of these rules out a diagnosis of hyperkinetic disorder.