Introduction to ADHD.
Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, impulsivity and hyperactivity that are inconsistent with the child’s developmental level.
For a diagnosis, the behaviours and difficulties associated with ADHD must interfere significantly with an individual’s functioning. In this sense, ADHD is associated with a huge variety of problems including poor academic performance, interpersonal relationship difficulties and, later in life, employment problems.
There are two diagnostic criteria in common use, the Diagnostic and Statistical Manual of Mental Disorders 5th Edition (DSM-5) and the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10). These criteria differ in their classification of ADHD. Both, DSM-5 and ICD-10, were developed as guidance for healthcare practitioners but not as a specific algorithm.
The DSM-5 criteria, defined by the American Psychiatric Association (2013), include three subtypes of ADHD: predominantly inattentive, predominantly hyperactive/impulsive, and combined presentation.
Regarding the DSM-5 criteria, six (or more) symptoms from each subtype are required for a diagnosis in children patients, whereas for older adolescents and adults (age 17 and older), at least the presence of five symptoms are required. Symptoms must have persisted for at least six months to a degree that is inconsistent with the child’s developmental level and have caused impairment directly on social and academic/occupational activities. These criteria are widely used and can be evaluated through the following tests: the SNAP-IV (Swanson, 1992), BAARS-IV (Barkley, 2011), ADHD Rating Scale-IV (DuPaul et al, 1998), and Kiddie-Sads-Present and Lifetime Version (K-SADS-PL; Kaufman et al., 1996). DSM-5 does not permit to diagnose patients under 12 years old.
The ICD-10 criteria, defined by the World Health Organization (1992), diagnoses ADHD under the title Hyperkinetic Disorder. The symptoms remain the same as in the DSM-5, however, the nine hyperactivity/impulsivity symptoms of the DSM-5 are separated into their constituent parts, with five hyperactivity symptoms and four impulsivity symptoms. In contrast to the DSM-5, the ICD-10 does not outline different subtypes of Hyperkinetic Disorder. Regarding ICD-10, children must present at least six inattention symptoms, three hyperactivity symptoms and at least one impulsivity symptom to be diagnosed as a Hyperkinetic Disorder. The number of symptoms required for a diagnosis is not age dependent in the ICD-10, and this is the same for both children and adults. Similar to the DSM-5, the ICD-10 requires symptoms to have been present for at least six months to a degree that is inconsistent with typical developmental levels of that age, and to cause impairment across more than one situation. ICD-10 does not permit to diagnose under 7 years old.
Whilst ADHD can be diagnosed in children under the age of five (there is no minimum age proposed by the diagnostic guidelines), symptoms can be hard to distinguish from the variation seen in normative behaviours during pre-school years. Thus, it is recommended that assessors exercise caution when assessing ADHD in children younger than five.
Co-existing problems and disorders
For a diagnosis of ADHD, symptoms must not be better explained by another mental disorder (e.g. substance use, anxiety, depression), which involves an assessment for differential diagnoses. However, children with ADHD often present with a second psychiatric disorder; it is reported that up to two-thirds of children with ADHD have one or more co-existing conditions. Common comorbidities include oppositional defiant and conduct disorder, anxiety and mood disorders, tic disorders and autistic spectrum disorders (National Collaborating Centre for Mental Health (Great Britain), National Institute for Health and Clinical Excellence (Great Britain), British Psychological Society., & Royal College of Psychiatrists., 2009). Hence, the assessor must distinguish between primary (i.e. differential) and secondary (i.e. co-existing) conditions.
The classification systems differ on this criterion. The DSM-5 recognises and allows for comorbidities, whereas they are exclusion criteria in the ICD-10. This contributes to the preference among practitioners of the broader DSM-5 criteria as it fits more closely with clinical practice.
- American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington: American Psychiatric Association.
- Barkley, R. A. (2011). Barkley Adult ADHD Rating Scale – IV (BAARS-IV). New York: Guildford Press.
- DuPaul, G. J., Power, T. J., Anastopoulos, A. D., & Reid, R. (1998). ADHD Rating Scale-IV (for Children and Adolescents): Checklist, Norms, and Clinical Interpretation. New York: Guildford Press.
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- Kaufman, J., Birmaher, B., Brent, D., Rao, U., Flynn, C., Moreci, P., … & Ryan, N. (1997). Schedule for affective disorders and schizophrenia for school-age children – Present and lifetime version (K-SADS-PL): Initial reliability and validity data. Journal of the American Academy of Child and Adolescent Psychiatry, 36(7), 980-988.
- Kessler, R. C., Adler, L., Berkley, R., Biederman, J., Connors, C. K., Demler, O., … & Zaslavsky, A. M. (2006). The prevalence and correlates of adult ADHD in the United States: results from the national comorbidity survey replication. American Journal of Psychiatry, 163(4), 716-723.
- National Collaborating Centre for Mental Health (Great Britain), National Institute for Health and Clinical Excellence (Great Britain), British Psychological Society., & Royal College of Psychiatrists. (2009). Attention deficit hyperactivity disorder : diagnosis and management of ADHD in children, young people, and adults. British Psychological Society.
- Pliszka, S. R. (1998). Comorbidity of attention-deficit/hyperactivity disorder with psychiatric disorder: an overview. Journal of Clinical Psychiatry, 59(suppl.7), 50-58.
- Shaw, M., Hodgkins, P., Caci, H., Young, S., Kahle, J., Woods, A., & Arnold, L.G. (2012). A systematic review and analysis of long-term outcomes in attention deficit hyperactivity disorder: Effects of treatment and non-treatment. BMC Medicine, 10(99), 1-15.
- Swanson, J. M. (1992). School-based assessments and interventions for ADD students. Irvine: K. C. Press.
- World Health Organization. (1992). International Statistical Classification of Diseases and Related Health Problems (10th ed.). Geneva: World Health Organization.