Identifying subgroups of attention-deficit/hyperactivity disorder from the psychopathological and neuropsychological profiles

The Research Domain Criteria (RDoC) advocates the dimensional approach in characterizing mental disorders. We followed RDoC to characterize children with ADHD using profiling based on the cognitive and psychopathological domains. We aimed to identify and validate ADHD subtypes with different clinical characteristics and functional impairments. We recruited 362 drug-naïve children with ADHD and 103 typically developing controls. The cluster analysis was used to identify subgroups based on the Child Behaviour Checklist (CBCL) and the Behaviour Rating Inventory of Executive Function (BRIEF). The subgroups' clinical characteristics and functional impairments were assessed using the WEISS Functional Impairment Rating Scale-Parent Report (WFIRS-P) and the Conners Parent Symptom Questionnaire (PSQ). The cluster analysis yielded four subgroups: (1) ADHD with severe impairment in psychopathology and executive functions (EF), (2) ADHD with mild executive dysfunctions and normal-level psychopathology, (3) ADHD with severe externalizing problems and (4) ADHD with severe executive dysfunctions. These subgroups showed different clinical characteristics and degrees of functional impairment. The EF impairment group displayed more serious learning problems and worse life skills than the externalizing group. The two groups with externalizing problems (i.e. the severe impairment group and the externalizing group) both exhibited higher rates of the combined subtype of ADHD and higher rates of comorbid ODD. Different subtypes of ADHD displayed different profiles of internalizing and externalizing problems and levels of executive dysfunctions. In particular, the subtype with severe impairment in EF exhibited more learning problems and worse life skills, suggesting EF is a critical target for intervention in children with ADHD.