OBJECTIVETo study the features of various subtypes of attention deficit hyperactivity disorders (ADHD) in children.

METHODSSex composition, risk factors, comorbidities, intelligence quotient and behavioral problems were investigated in 175 children with ADHD who met the Diagnostic Statistical Manual of Mental Disorder Criteria (DSM-IV). The children were classified into three groups: ADHD predominantly inattentive (ADHD-I, n=82), ADHD predominantly hyperactive-impulsive (ADHD-HI, n=24) and ADHD combined type (ADHD-C, n=69).

RESULTSThere were no significant differences in the sex composition among the three groups. The rates of birth abnormality in the ADHD-I and the ADHD-C groups were higher than those in the ADHD-HI group. Negative parenting practices were noted more frequently in the ADHD-HI and the ADHD-C groups than the ADHD-I group. There were no significant differences in the performance intelligence quotient (PIQ), verbal intelligence quotient (VIQ) and full intelligence quotient (FIQ) among the three groups. However, the incidence of imbalance between VIQ and PIQ in the ADHD-I group was higher than the other two groups. The rate of comorbidities with oppositional defiant disorder (ODD) and tic disorder (TD) in the ADHD-C and the ADHD-HI groups was higher than that in the ADHD-I group. Both the ADHD-I and the ADHD-C groups had a higher rate of comorbidities with learning disorder (LD) than the ADHD-HI group. The impulsive/hyperactive and conduct problems were more severe and the hyperactivity index was higher in the ADHD-C and the ADHD-HI groups than those in the ADHD-I group, while the learning difficulties in the ADHD-I group were the most severe.

CONCLUSIONSThe children with ADHD-C or ADHD-HI have higher incidences of comorbidities with ODD and TD than those with ADHD-I who the learning difficulties and the imbalance between VIQ and PIQ are more severe.