Attention-deficit hyperactivity disorder overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Charmaine Patel, M.D. [2]

Overview

Attention deficit hyperactivity disorder is a disorder characterized by inattentiveness, hyperactivity, and impulsivity. It starts in childhood before the age of seven, and has a strong component of heritability. The condition seems to be more common in boys, but this may be because the symptoms are less recognizable in females.

Pathophysiology

Attention deficit hyperactivity disorder appears to be highly heritable, although one-fifth of all cases are estimated to be caused from trauma or toxic exposure. Evidence suggests that hyperactivity has a strong heritable component, and in all probability ADHD is a heterogeneous disorder, meaning that several causes could create very similar symptomology.. Although there is evidence for dopamine abnormalities in ADHD, it is not clear whether abnormalities of the dopamine system are the molecular abnormality of ADHD or a secondary consequence of a problem elsewhere.

Differentiating Attention Deficit Hyperactivity Disorder from other Conditions

Attention deficit hyperactivity disorder (ADHD) can be differentiated from other psychiatric disorders by following DSM-IV criteria. Aspects of ADHD that make it distinguishable, is that some symptoms must be present before the age of 7 years old. Also, the symptoms of inattention, hyperactivity, and distractability are consistently present over time, which is unlike mania in bipolar disorder, or drug use.

Epidemiology and Demographics

A review of 102 studies estimated ADHD's worldwide prevalence in people under the age of 19 to be 5.29%. 10% of males, and 4% of females have been diagnosed in the U.S.

Risk Factors

Several factors have been implicated as risk factors in the development of ADHD. Maternal smoking and alcohol use have had an association to the development of ADHD in the child. In addition, high blood lead levels have been linked to ADHD.

Natural History, Complications and Prognosis

Symptoms of ADHD usually begin before the age of 7 years old, although the symptoms may be less apparent in females. Symptoms are not usually severe, however they can cause a significant impairment in social and occupational functioning. Adults are able to hide the symptoms more easily. Children who are not medicated for ADHD have higher rates of substance abuse in adulthood. Paradoxically, stimulant medications are intoxicants, and substance dependence may develop.

Diagnosis

Diagnosis of ADHD is based on DSM IV criteria. These are very specific criteria which assess the patient's functioning and the impact of their symptoms on their life, in various settings. History includes symptoms of innattentiveness, hyperactivity, impulsivity, difficulty functioning at school and at an occupational level, and difficulty with organization. Symptoms may also affect relationships in the social setting.

Treatment

First line treatments include stimulant medications such as methyphenidate and dextroamphetamine. More recent, less addictive medications used is modafinil. Behavioral modification and strategies have also been shown to help, as pharmacologic treatment is thought to mostly help symptoms associated with poor concentration.