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.
| Attention deficit hyperactivity disorder | |
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| People with ADHD struggle more than others to sustain their attention on some tasks (such as schoolwork), but may maintain an unusually intense level of attention for tasks they find immediately rewarding or interesting. | |
| Specialty |
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| Symptoms |
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| Usual onset | Typically at least some ADHD symptoms and impairments onset during the developmental period. Exceptions include if they were compensated for (e.g., by a high IQ or structured environment) or if the individual clearly suffered a neurologically compromising event. |
| Causes | Genetic (inherited, de novo) and to a lesser extent, environmental factors (exposure to biohazards during pregnancy, traumatic brain injury) |
| Diagnostic method | Based on symptoms after other possible causes have been ruled out |
| Differential diagnosis |
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| Treatment |
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| Medication |
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| Frequency | 0.8–1.5% (2019, using DSM-IV-TR and ICD-10) |
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 and a direct average reduction in life expectancy of 13 years. 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 persist on tasks with temporally delayed consequences, they may be able to maintain an unusually prolonged level of attention for tasks they do find intrinsically interesting or immediately rewarding; this is known as hyperfocus (more colloquially) or perseverative responding. This is a mental state in which a person is completely absorbed in a task to the point of apparently ignoring or "tuning out" everything else, often with difficulty disengaging and can be related to risks such as for internet addiction and types of offending behaviour.
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.
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.