Attention-deficit hyperactivity disorder (ADHD) is a neuropsychological developmental disorder in which children (and adults) are more inattentive, distractible, impulsive and hyperactive than what is normal for their age (Banich, 2004, p. 449; Barkley, 1998, p. 67; Swanson et al., 1998, p. 446). The disorder is characterized by three kinds of behavioral symptoms (Shaywitz, Fletcher, Pugh, Klonnan, & Shaywitz, 1999, p.185) in two cognitive domains, inattention and impulsivity, along with a motor domain, hyperactivity (Swanson et al., 1998, pp. 446, 447). It is estimated that between 2 and 9.5 of all school children worldwide have ADHD (Barkley, 1998, p. 67).
The American Psychological Association’s (APA) Diagnostic and Statistical Manual (DSM-IV) includes nine symptoms in the domain of inattention and nine in the domains of hyperactivity/impulsivity. In order to warrant a diagnosis, six of these symptoms must have an early onset (by age seven), must be present for at least six months (must be chronic), must occur in at least two settings, and must cause impairment to academic, social or occupational functioning (Barkley, 1998, p. 68; Swanson et al., 1998, p. 447). Three types of disorders stem out of this definition: predominantly inattentive, primarily impulsive/hyperactive, and combined.
ADHD can cause severe problems in academic and social functioning, as well as for working environments. Symptoms of ADHD can impair "family life, peer relationships and the ability to succeed in school" (Kumra & Thaden, 2004, p. 40). The following quote illustrates how ADHD can profoundly influence someone’s life: "i can say from my personal experience is that i was always an underachiever with adhd. and i was the type of person who no body liked. i was too wild and said stupid things constantly." (truthandgrace, no date)