Assessment of functioning in ADHD according to World Health Organization standards: First revision of the International Classification of Functioning, Disability and Health Core Sets.

AIM: To conduct the first revision of the World Health Organization International Classification of Functioning, Disability and Health (ICF) Core Sets for attention-deficit/hyperactivity disorder (ADHD).

METHOD: A Delphi-like method was used, integrating evidence from stakeholder feedback and developing and piloting the ADHD ICF Core Set platform to inform revisions to the ADHD Core Sets.

RESULTS: A total of 27 second-level ICF codes were added to the comprehensive ADHD Core Set: body functions of temperament and personality, and basic sensory functions; activities and participation in terms of learning to read and write, spoken communication, community life, religion and spirituality, education, economy, and human rights; environmental factors for domestic animals; and several societal services. The revised comprehensive Core Set contains 98 ICF codes: 18 body function codes; 47 activities and participation codes; and 33 environmental factor codes. Extensive changes were also made to the age-appropriate brief Core Sets to allow their independent use in research and clinical practice.

INTERPRETATION: Although substantially expanded, the revised ICF Core Sets better reflect the lived experience of individuals with ADHD and clinical implementation preferences than the initial sets. We recommend further feasibility and validation studies of these Core Sets with the goal of optimizing their acceptance and practicability, and strengthening their evidence base.