Attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by executive dysfunction occasioning symptoms of inattention, hyperactivity, impulsivity and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and otherwise age-inappropriate.

ADHD symptoms arise from executive dysfunction, and emotional dysregulation is often considered a core symptom. Difficulties with self-regulation such as time management, inhibition and sustained attention may result in poor academic performance, unemployment and numerous health risks, collectively predisposing to a diminished quality of life. ADHD is associated with other neurodevelopmental and mental disorders as well as some non-psychiatric disorders, which can cause additional impairment, especially in modern society. Although people with ADHD struggle to sustain attention on tasks that entail delayed rewards or consequences, they are often able to maintain an unusually prolonged and intense level of attention for tasks they do find interesting or rewarding; this is known as hyperfocus.

ADHD represents the extreme lower end of the continuous (bell curve) dimensional trait of executive functioning and self-regulation, which is supported by twin, brain imaging and molecular genetic studies.

The precise causes of ADHD are unknown in the majority of cases. For most people with ADHD, many genetic and environmental risk factors accumulate to cause the disorder. The environmental risks for ADHD most often exert their influence in the prenatal period. However, in rare cases a single event might cause ADHD such as traumatic brain injury, exposure to biohazards during pregnancy, a major genetic mutation or extreme environmental deprivation early in life. There is no biologically distinct adult onset ADHD except for when ADHD occurs after traumatic brain injury.

Genetic factors play an important role; ADHD tends to run in families and has a heritability rate of 70-80%. The remaining 20-30% of variance is mediated by de-novo mutations and non-shared environmental factors that provide for or produce brain injuries. Very rarely, ADHD can also be the result of abnormalities in the chromosomes.

It affects about 5–7% of children when diagnosed via the DSM-IV criteria, and 1–2% when diagnosed via the ICD-10 criteria. Rates are similar between countries and differences in rates depend mostly on how it is diagnosed. ADHD is diagnosed approximately twice as often in boys as in girls, and 1.6 times more often in men than in women, although the disorder is overlooked in girls or diagnosed in later life because their symptoms sometimes differ from diagnostic criteria. About 30–50% of people diagnosed in childhood continue to have ADHD in adulthood, with 2.58% of adults estimated to have ADHD which began in childhood. In adults, hyperactivity is usually replaced by inner restlessness, and adults often develop coping skills to compensate for their impairments. The condition can be difficult to tell apart from other conditions, as well as from high levels of activity within the range of normal behaviour. ADHD has a negative impact on patient health-related quality of life that may be further exacerbated by, or may increase the risk of, other psychiatric conditions such as anxiety and depression.

ADHD management recommendations vary and usually involve some combination of medications, counseling, and lifestyle changes. The British guideline emphasises environmental modifications and education about ADHD for individuals and carers as the first response. If symptoms persist, parent-training, medication, or psychotherapy (especially cognitive behavioural therapy) can be recommended based on age. Canadian and American guidelines recommend medications and behavioural therapy together, except in preschool-aged children for whom the first-line treatment is behavioural therapy alone. Medications are the most effective pharmaceutical treatment, although there may be side effects and any improvements will be reverted if medication is ceased.

ADHD, its diagnosis, and its treatment have been considered controversial since the 1970s. These controversies have involved doctors, teachers, policymakers, parents, and the media. Topics have included causes of ADHD and the use of stimulant medications in its treatment. ADHD is now a well-validated clinical diagnosis in children and adults, and the debate in the scientific community mainly centers on how it is diagnosed and treated. ADHD was officially known as attention deficit disorder (ADD) from 1980 to 1987; prior to the 1980s, it was known as hyperkinetic reaction of childhood. Symptoms similar to those of ADHD have been described in medical literature dating back to the 18th century.