ADHD is one of the most commonly diagnosed behavioral disorders of childhood. The disorder is estimated to affect between 6 to 16 out of every 100 school-aged children . This makes ADHD a major health concern. The disorder does not affect only children. In many cases, problems continue through adolescence and adulthood.
The core symptoms of ADHD are developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. These problems are persistent and usually cause difficulties in one or more major life areas: home, school, work, or social relationships. Clinicians base their diagnosis on the presence of the core characteristics and the problems they cause.
Not all children and youth have the same type of ADHD. Because the disorder varies among individuals, children with ADHD won't all have the same problems. Some may be hyperactive. Others may be under-active. Some may have great problems with attention. Others may be mildly inattentive but overly impulsive. Still others may have significant problems in all three areas (attention, hyperactivity, and impulsivity). Thus, there are three subtypes of ADHD:
Of course, from time to time, practically every person can be a bit absent-minded, restless, fidgety, or impulsive. So why are these same patterns of behavior considered normal for some people and symptoms of a disorder in others? It's partly a matter of degree. With ADHD, these behaviors occur far more than occasionally. They are the rule and not the exception.