What is ADHD

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ADHD is a neurodevelopmental disorder that manifests as a persistent pattern of inattention and/or hyperactivity/impulsivity, in 2 or more settings, that is inconsistent with what is typically seen in other people at a comparable level of development.1 There is clear evidence that the symptoms interfere with, or reduce the quality of, social, academic, and/or occupational functioning.

The current Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5®) specifies 3 core symptoms of ADHD1:

  • Inattention
  • Hyperactivity
  • Impulsivity

These are not the only criteria used to diagnose ADHD. Diagnosis should be based on a complete history and evaluation of the patient.

Individuals with ADHD often have difficulty focusing, are easily distracted, have trouble staying still, and frequently are unable to control their impulsive behavior.1 It can also affect teenagers and adults.2

Although the exact origin of ADHD is not known, researchers believe that ADHD may be caused by one or more of several factors:

Neurotransmitter Function: ADHD is thought to be caused by an imbalance of dopamine and norepinephrine in the brain. Scientists think that these chemicals might play an important role in ADHD.3

Genetic Factors: Research suggests that ADHD tends to run in families. However, this does not mean that all children in a family will have the disorder.4

Environment: Certain external factors, such as smoking during pregnancy or complications during pregnancy and/or delivery, or infancy, may contribute to ADHD.5,6


  1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. (DSM-5®). Arlington, VA: American Psychiatric Publishing; 2013.
  2. Pliszka S; AACAP Work Group on Quality Issues. Practice parameter for the assessment and treatment of children and adolescents with attention-deficit/hyperactivity disorder. J Am Acad Child Adolesc Psychiatry. 2007;46(7):894-921.
  3. Arnsten AF, Li BM. Neurobiology of executive functions: catecholamine influences on prefrontal cortical functions. Biol Psychiatry. 2005;57(11):1377-1384.
  4. Biederman J, Faraone SV. Attention-deficit hyperactivity disorder. Lancet. 2005;366(9481):237-248.
  5. Gustafsson P, Källén K. Perinatal, maternal, and fetal characteristics of children diagnosed with attention-deficit-hyperactivity disorder: results from a population-based study utilizing the Swedish Medical Birth Register. Dev Med Child Neurol. 2011;53(3):263-268.
  6. Rodriguez R, Bohlin G. Are maternal smoking and stress during pregnancy related to ADHD symptoms in children? J Child Psychol Psychiatry. 2005;46(3):246-254.