How is ADHD diagnosed?
When evaluating individuals for attention-deficit hyperactivity disorder (ADHD), or hyperkinetic disorder (HKD), it is typical to use multiple stages of assessment prior to formal diagnosis, including1-5:
- Clinical assessments
- Assessment tools and rating scales
- Clinical interviews with the individuals and parents/teachers for children and adolescents or partners for adults with ADHD.
The National Institute for Health and Care Excellence (NICE) guidelines state that a diagnosis of ADHD should only be made by a specialist psychiatrist, paediatrician or other appropriately qualified healthcare professional with training and expertise in the diagnosis of ADHD. Diagnosis of ADHD should also be based upon a full clinical and psychosocial assessment, a full developmental and psychiatric history, and observer reports of the individual’s mental state. According to the NICE guidelines, for a diagnosis of ADHD, symptoms of hyperactivity-impulsivity and/or inattention should meet the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM) for ADHD and the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) for HKD.1 Note that in 2018, the ICD-10 was updated to the International Classification of Diseases 11th Revision (ICD-11), where HKD is now referred to as ADHD.6
Regardless of which medical classification system is used, the features of ADHD described are similar, with both sets of diagnostic criteria describing ADHD as a pattern of inattention and/or hyperactivity-impulsivity (combined, predominantly inattentive or predominantly hyperactive-impulsive presentations).6,7 Nevertheless, these medical classification systems should be used in conjunction with a range of rating scales, which often measure the impact of ADHD upon more specific areas of functioning or quality of life.1-4
How do the two classification systems define ADHD?
The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM)
The DSM-5TM medical classification system for ADHD is published by the American Psychiatric Association, and is used in the US and the rest of the world. This classification system defines ADHD as “a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development”.7 The DSM-5TM includes ADHD among neurodevelopmental disorders, which comprise conditions associated with factors affecting brain development, and gives examples of how ADHD symptoms are expressed across the lifespan. The DSM-5TM states that at least five symptoms must be present prior to age 12 years, and that there should be clear evidence that symptoms interfere with or reduce the level of social, academic and occupational functioning for a diagnosis of ADHD.5
The DSM-5TM replaced the previous version (DSM-IV) in 2013.7,8 The NICE guidelines1 and other clinical guidelines2-5 refer to the DSM-5TM; however, some clinical trials initiated before the new edition also refer to the DSM-IV.
International Classification of Diseases 11th Revision (ICD-11)
Published in 2018, the ICD-11 characterises ADHD as a “persistent pattern (at least 6 months) of inattention and/or hyperactivity-impulsivity that has a direct negative impact on academic, occupational or social functioning.”6
The ICD-11 further states that the onset of these symptoms occurs prior to age 12 years, typically by early- to mid-childhood. The degree of inattention and hyperactivity-impulsivity is also outside the limits of normal variation expected for age and level of intellectual functioning, and has a direct negative impact on academic, occupational or social functioning.6
According to the ICD-11, ADHD can present as6:
- Predominantly inattentive
- Some hyperactive-impulsive symptoms may also be present, but these are not clinically significant in relation to the inattentive symptoms.
- Predominantly hyperactive-impulsive
- Some inattentive symptoms may also be present, but these are not clinically significant in relation to the hyperactive-impulsive symptoms.
- Both inattentive and hyperactive-impulsive symptoms are clinically significant, with neither predominating in the clinical presentation.
The ICD-11 indicates that since the balance and specific manifestations of ADHD may vary across individuals, and may change over the course of development, the symptoms must be observable in more than one setting in order for a diagnosis of ADHD to be made.6
- NICE guideline 2018. Attention deficit hyperactivity disorder: diagnosis and management. Available at: https://www.nice.org.uk/guidance/ng87. Accessed January 2021.
- Canadian ADHD Resource Alliance (CADDRA). Canadian ADHD Practice Guidelines. Edition 4.1. Toronto, ON: CADDRA, 2020.
- Banaschewski T, Hohmann S, Millenet S. Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS) im Kindes-, Jugend- und Erwachsenenalter. DGKJP, DGPPN and DGSPJ German guidelines. 2018.
- Guías de Práctica Clínica en el SNS. Grupo de trabajo de la Guía de Práctica Clínica sobre las Intervenciones Terapéuticas en el Trastorno por Déficit de Atención con Hiperactividad (TDAH). 2017.
- Kooij JJS, Bijlenga D, Salerno L, et al. Updated European Consensus Statement on diagnosis and treatment of adult ADHD. Eur Psychiatry 2019; 56: 14-34.
- World Health Organization. ICD-11: International Classification of Diseases 11th Revision. 2018. Available at: https://icd.who.int/. Accessed January 2021.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. 2013.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Washington, DC: American Psychiatric Association, 2004.