Attention Deficit Hyperactivity Disorder (ADHD) represents a frequent and highly comorbid disorder in children and adolescents. Comorbidity differs according to ADHD subtype and gender and has been reported to have a direct effect on the severity of ADHD.A descriptive, cross-sectional study was designed to determine the patterns of ADHD comorbidity in 102 children, aged 6 to 12 years, who attend the outpatient services of a child psychiatric hospital in Mexico City. The evaluation was performed using the Child Behavior Checklist (CBCL).The sample had about five comorbid disorders. The hyperactive-impulsive subtype had more severe externalizing symptoms, while the combined subtype had a higher severity of anxious depressive symptoms, delinquent behavior and internalized symptoms. Somatic complaints were more frequent in boys. A linear regression analysis showed that the severity of attention problems was influenced by the severity of aggressive behavior.School age children who came to psychiatric attention services with ADHD are highly comorbid. The comorbidity increases the severity of attention problems, particularly in patients with the hyperactive-impulsive or combined subtypes.
