Attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder
Other names	Formerly: Attention deficit disorder (ADD), hyperkinetic disorder (HD)[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	Psychiatry pediatrics
Symptoms	Inattention hyperactivity disinhibition executive dysfunction emotional dysregulation impulsivity impaired working memory
Usual onset	In most cases at least some ADHD symptoms and impairments 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) non-stimulants (atomoxetine, viloxazine) alpha-2A agonists (guanfacine XR, clonidine XR)
Frequency	0.8–1.5% (2019, using DSM-IV-TR and ICD-10)[3]

Attention-deficit/hyperactivity disorder (ADHD)^[4] is a neurodevelopmental disorder characterized by executive dysfunction occasioning symptoms of inattention, hyperactivity, impulsivity and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and developmentally-inappropriate.^[10]

ADHD symptoms arise from executive dysfunction,^[19] and emotional dysregulation is often considered a core symptom.^[23] Impairments resulting from deficits in self-regulation such as time management, inhibition, and sustained attention^[24] can include poor professional performance, relationship difficulties, and numerous health risks,^[25][26] collectively predisposing to a diminished quality of life^[27] and a direct average reduction in life expectancy of 13 years.^[28][29] The disorder costs society hundreds of billions of US dollars each year, worldwide.^[30] It is associated with other neurodevelopmental and mental disorders as well as non-psychiatric disorders, which can cause additional impairment.^[9]

While people with ADHD often struggle to initiate work and persist on tasks with delayed consequences, this may not be evident in contexts they find intrinsically interesting and immediately rewarding,^[31][18] potentiating hyperfocus (a more colloquial term)^[32] or perseverative responding.^[33] This mental state is often hard to disengage from^[34][35] and is related to risks such as for internet addiction^[36] and types of offending behaviour.^[37]

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][14][39][18][40][41][42][43]}

The precise causes of ADHD are unknown in most individual cases.^[44][45] Meta-analyses of studies of twins, families and molecular genetics have shown that the disorder is primarily genetic with a heritability rate of 70-80%,^[46] where risk factors are highly accumulative.^[47] The environmental risks are not related to social or familial factors;^[48][49][50] they exert their effects very early in life, in the prenatal or early postnatal period.^[9] However, in rare cases, ADHD can be caused by a single event including traumatic brain injury,^{[46][51][52][53]} exposure to biohazards during pregnancy,^[9] or a major genetic mutation.^[54] There is no biologically distinct adult-onset ADHD except for when ADHD occurs after traumatic brain injury.^[55][9]