Comorbidity in hyperactive children: issues related to selection bias, gender, severity, and internalizing symptoms.

Parental behavior ratings of hyperactive boys and girls aged 6-11 years seen for evaluation in a general outpatient child psychiatry clinic and in a specialty "attention deficit disorder" (ADD) program were analyzed. The pattern of comorbidity in the two groups showed no significant differences. Most of the associated internalizing and externalizing behavioral scales in hyperactive boys and in hyperactive girls were elevated and in clinical ranges except for the "somatic complaints" scale. Comorbidity in both hyperactive boys and girls was related to the severity of the hyperactivity itself.