Psychiatric comorbidity and functioning in clinically referred preschool children and school-age youths with ADHD

Although the literature documents that attention-deficit/hyperactivity disorder (ADHD) commonly onsets prior to age 6, little is known about the disorder in preschool children. We evaluated the clinical characteristics, psychiatric comorbidity, and functioning of preschool children and school-age youths with ADHD referred to a pediatric psychiatric clinic for evaluation.

Structured psychiatric interviews assessing lifetime psychopathology by DSM-III-R criteria were completed with parents about their children. Family, social, and overall functioning were also assessed at intake.

We identified 165 children with ADHD aged 4 to 6 years (preschool children) and 381 youths aged 7 to 9 years (school-age) with ADHD. Despite being younger, preschool children had similar rates of comorbid psychopathology compared with school-age youths with ADHD. There was an earlier onset of ADHD and co-occurring psychopathology in the preschool children compared to school-age youths. Both preschool children and school-age youths had substantial impairment in school, social, and overall functioning.

The results of this study suggest that despite being significantly younger, clinically referred preschool children with ADHD are reminiscent of school-age youths with ADHD in the quality of ADHD, high rates of comorbid psychopathology, and impaired functioning. Follow-up of these clinically referred preschool children with ADHD to evaluate the stability of their diagnoses, treatment response, and their long-term outcome are necessary.