Abstract

Diagnostic guidelines differ between DSM attention-deficit/hyperactivity disorder (ADHD) and ICD hyperkinetic disorder (HKD). Only 145 of 579 children age 7–9 in the Multimodal Treatment Study of ADHD (the MTA) with combined-type DSM-IV ADHD met criteria for ICD-10 HKD, because major internalizing comorbidities and more stringent symptom count/pervasiveness requirements excluded most. The 145 HKD had significantly better 14-month medication response than the rest. We explored whether HKD had greater adult symptom persistence and/or impairment than other ADHD. Multi-informant assessments were done for 16 years. We used the 12/14/16-year assessments, in young adulthood. The post-attrition 109 with baseline HKD had no greater adult persistence of ADHD symptoms/impairment than 367 without HKD, but had more cumulative stimulant use, more job losses, lower emotional lability, and fewer car crashes. However, those excluded for internalizing comorbidity but otherwise meeting HKD criteria had significantly more persistence. Only 6 of the 109 (5.5%) with baseline HKD met ICD-10 criteria for HKD in adulthood, compared to 25 of 367 (6.8%) without a childhood HKD diagnosis. Despite greater initial symptom severity, HKD had no worse 16-year young adult outcome than others, except for job losses, balanced by less emotional lability and fewer crashes. Comorbid internalizing disorder seems to have worse prognosis than initial severity/pervasiveness of ADHD symptoms.