Neurobiology of Attention Deficit Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental psychiatric disorder characterized by deficits in attention and hyperactivity-impulsivity. These symptoms have been associated with impaired academic performance, low self-esteem, negative occupational outcomes, lower adaptive functioning, social skills problems, aggressive and risky behaviors, and accidental injuries. Both genes and environment, or their interaction, increase the risk of the disorder. Due to the multifactorial causes underlying the disorder, ADHD has a heterogeneous presentation, affecting different cognitive domains, and is frequently co-occurring with psychiatric and medical comorbidities. Neuroimaging studies have reported modestly decreased cortical thickness and reduced volumes of subcortical brain regions in children with ADHD, but not in adolescents or adults. The observed neuroimaging differences are small and cannot be used for diagnostic purposes. Pharmacological treatments reduce symptoms in clinical trials and, in observational studies, show beneficial effects for educational underachievement, accidental injuries, and risky behaviors. Guidelines recommend stimulants as the first-line treatment for individuals with ADHD except for children younger than 6. Non-medication treatments for ADHD are less effective but are useful to help with problems that remain after the medication treatment has been optimized.