Attention deficit hyperactivity disorder (ADHD) was first described more than 100 years ago. Characterized by excessively inattentive, hyperactive, or impulsive behaviors, ADHD affects an estimated 5 to 8 percent of school-age children. Studies show that as many as 60 percent of these children will continue to experience ADHD symptoms as adults. Children with ADHD are more likely to have problems in school, graduating from high school, maintaining a job, abusing drugs, or having healthy relationships.
Symptoms of ADHD appear by middle childhood, last for six months or longer, and impair normal functioning to a significant degree in the following settings: for children — at school, among friends, and at home; for adults — at work and at home. Currently, no objective diagnostic test for ADHD exists. Diagnosis requires a comprehensive evaluation, including a clinical interview, parent and teacher ratings for children, and self and other ratings for adults. Learning disorder and psychological testing may also be used to clarify if other disorders are present along with the ADHD or if other conditions that look like ADHD may be responsible for the behaviors in question. Thorough evaluation is required because problems with attention can be triggered by many other conditions; in particular, adults may have attention issues along with other disorders such as depression.
Twin and family studies show that ADHD has a strong genetic influence, and genes encoding components of dopamine and norepinephrine transmission have been implicated. Increasingly, studies are finding correlations between ADHD and differences in brain function. Altered activity is often observed in circuits connecting the cortex, the striatum, and the cerebellum, particularly in the right hemisphere. Recent studies show a delay in cortical development in some children with ADHD, although most individuals with ADHD do not outgrow the disorder as they mature. Rather, their symptoms often change as they grow older, with less hyperactivity as adults. Problems with attention tend to continue into adulthood.
Recent imaging studies have shown reduced catecholamine transmission in at least some patients with this disorder. Because prefrontal circuits require an optimal level of catecholamine stimulation, reduced catecholamine transmission could lead to weakened prefrontal cortical regulation of attention and behavior and symptoms of ADHD.
ADHD is commonly treated with parent education, school-based interventions, and medications such as stimulants (e.g., methylphenidate) and newer, nonstimulant drugs. Adults benefit from the same medications as children and may find some behavioral therapies helpful. The medications all act by enhancing catecholamine transmission.
There is no cure for ADHD at this time. Treatment effectiveness should be re-evaluated in each person on a regular basis to determine if the current treatment continues to be optimal.