Attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder
Other names	Attention-deficit/hyperactivity disorder Formerly: Attention deficit disorder (ADD), hyperkinetic disorder[1]
ADHD arises from maldevelopment in brain regions such as the prefrontal cortex, basal ganglia and anterior cingulate cortex, which regulate the executive functions necessary for human self-regulation.
Specialty	Neuropsychiatry pediatrics
Symptoms	Inattention hyperactivity disinhibition executive dysfunction emotional dysregulation impulsivity impaired working memory
Usual onset	Prior to age 12
Causes	Genetic (inherited, de novo) and to a lesser extent, environmental factors (exposure to biohazards during pregnancy, traumatic brain injury)
Diagnostic method	Based on impairing symptoms after other possible causes have been ruled out
Differential diagnosis	Bipolar disorder cognitive disengagement syndrome conduct disorder major depressive disorder autism spectrum disorder oppositional defiant disorder learning disorder intellectual disability anxiety disorder[2] borderline personality disorder fetal alcohol spectrum disorder
Treatment	Medication psychotherapy
Medication	Stimulants (methylphenidate, amphetamine) selective norepinephrine reuptake inhibitors (atomoxetine, viloxazine) α2A-adrenergic receptor agonists (guanfacine XR, clonidine XR)
Frequency	0.8–1.5% (2019, using DSM-IV-TR and ICD-10)[3]

Attention deficit hyperactivity disorder (ADHD)^[1] is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and developmentally inappropriate.^[9] ADHD symptoms arise from executive dysfunction.^[18]

Impairments resulting from deficits in self-regulation such as time management, inhibition, task initiation, and sustained attention^[19] can include poor professional performance, relationship difficulties, and numerous health risks,^[20][21] collectively predisposing to a diminished quality of life^[22] and a reduction in life expectancy.^[23][24] As a consequence, the disorder costs society hundreds of billions of US dollars each year, worldwide.^[25] It is associated with other mental disorders as well as non-psychiatric disorders, which can cause additional impairment.^[8]

While ADHD involves a lack of sustained attention to tasks,^[17][20] inhibitory deficits also can lead to difficulty interrupting an already ongoing response pattern, manifesting in the perseveration of actions despite a change in context whereby the individual intends the termination of those actions.^[26][27] This symptom is known colloquially as hyperfocus^[28] and is related to risks such as addiction^[29][30] and types of offending behaviour.^[31] ADHD can be difficult to tell apart from other conditions.^[16][22] ADHD represents the extreme lower end of the continuous dimensional trait (bell curve) of executive functioning and self-regulation, which is supported by twin, brain imaging and molecular genetic studies.^[38]

The precise causes of ADHD are unknown in most individual cases.^[39][40] Meta-analyses have shown that the disorder is primarily genetic with a heritability rate of 70–80%,^[41][42][43] where risk factors are highly accumulative.^[44] The environmental risks are not related to social or familial factors;^[45][46][47] they exert their effects very early in life, in the prenatal or early postnatal period.^[8] However, in rare cases, ADHD can be caused by a single event including traumatic brain injury,^{[41][48][49][50]} exposure to biohazards during pregnancy,^[8] or a major genetic mutation.^[51] As it is a neurodevelopmental disorder, there is no biologically distinct adult-onset ADHD except for when ADHD occurs after traumatic brain injury.^[8][52]