Attention-deficit/hyperactivity disorder (ADHD) !

ADHD is a brain development condition with lasting inattention, hyperactivity and impulsivity that starts in childhood and often continues into adulthood.

Updated 2026-11-01

Structures involved

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In embryology

Alcohol: fetal alcohol spectrum disorder

What it is

A neurodevelopmental disorder with a persistent pattern of inattention and/or hyperactivity-impulsivity that is excessive for the person's developmental level, begins before age 12 and impairs functioning in more than one setting (home, school, work).

Who gets it

One of the most common childhood mental disorders, affecting about 5% of children worldwide; studies in Colombia and Latin America report similar or higher figures depending on the method. Boys are diagnosed more often; girls more often have the inattentive type and are underdiagnosed. Symptoms persist into adulthood in a large share of cases.

Causes

Highly heritable (heritability around 70–80%)
Altered dopamine and noradrenaline signalling in frontostriatal circuits
Delayed maturation of the prefrontal cortex
Prenatal and early environmental insults (see risk factors)

Risk factors

Parent or sibling with ADHD
Prematurity and low birth weight
Prenatal exposure to tobacco, alcohol or other substances
Lead exposure in early childhood
Early severe deprivation or neglect

Pathophysiology

The prefrontal cortex and its connections with the striatum (caudate, putamen) and cerebellum control attention, planning and response inhibition. In ADHD these networks mature later and work less efficiently, with reduced dopamine and noradrenaline tone. The result is poor executive function: difficulty holding attention, stopping an impulse and organising tasks. Stimulants act by raising dopamine and noradrenaline in these circuits.

Classification

Predominantly inattentive presentation
Predominantly hyperactive-impulsive presentation
Combined presentation (the most common)
Severity: mild, moderate or severe

Symptoms and signs

Careless mistakes, trouble sustaining attention and not following through on tasks
Losing things, forgetfulness and being easily distracted
Fidgeting, leaving the seat, running or climbing at inappropriate times; in adults, inner restlessness
Talking excessively, blurting out answers, interrupting and difficulty waiting one's turn
Poor school or work performance despite adequate ability

Diagnosis

Clinical: Clinical diagnosis using DSM-5-TR criteria: at least six symptoms of inattention and/or hyperactivity-impulsivity (five from age 17) for six months or more, several present before age 12, in two or more settings, with clear impairment. Rating scales completed by parents and teachers (e.g. Vanderbilt, Conners) support it; screening for coexisting disorders is part of the assessment.
Tests: No blood test or scan diagnoses ADHD. Vision and hearing checks; thyroid tests, lead level or sleep study only if suggested by history. Before stimulants: cardiac history, blood pressure and heart rate; ECG if there is personal or family cardiac history.
Imaging: Not used for diagnosis.

Differential diagnosis

Learning disorders and intellectual disability
Autism spectrum disorder (they often coexist)
Anxiety, depression or bipolar disorder
Hearing or vision problems, sleep disorders (including obstructive sleep apnoea)
Hyperthyroidism, absence epilepsy, lead poisoning or substance use

Goal of treatment

Improve attention, behaviour and functioning at home, school and work, and support self-esteem and relationships, combining behavioural, educational and medication measures adapted to age.

Treatment

Conservative: Parent training in behaviour management is first-line for preschool children; behavioural classroom interventions, school accommodations and, in adolescents and adults, cognitive behavioural therapy and organisational skills training.
Medical: Stimulants (methylphenidate and amphetamine derivatives) are the most effective drugs from school age onward. Non-stimulants include atomoxetine (a noradrenaline reuptake inhibitor) and alpha-2 agonists (guanfacine, clonidine).
Follow-up: Nursing and medical follow-up of appetite, weight and height, sleep, heart rate and blood pressure, tics and mood; watch for misuse or diversion of stimulants. Atomoxetine needs monitoring for suicidal thoughts.
Lifestyle: Regular routines, adequate sleep, physical activity and limited screen time support other treatments.

Complications

School failure and dropout
Injuries and traffic accidents
Substance use disorders
Oppositional defiant and conduct disorder; later antisocial behaviour
Low self-esteem, depression and anxiety

Prognosis

Hyperactivity tends to lessen with age, while inattention more often persists. Many adults still have impairing symptoms. Treatment improves school results and lowers the risk of injuries and substance use.

Test yourself

Think of the answer, then tap the question to see it.

Before what age must several ADHD symptoms be present, and in how many settings?

Before age 12, in two or more settings (e.g. home and school).

Which drug class is first-line for ADHD in school-age children?

Stimulants (methylphenidate or amphetamine derivatives), combined with behavioural measures.

What is the first-line treatment for ADHD in preschool children?

Parent training in behaviour management.

Which growth and vital-sign parameters should be monitored on stimulants?

Weight and height (appetite suppression), heart rate and blood pressure, and sleep.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Attention Deficit Hyperactivity Disorder (MedlinePlus, US National Library of Medicine, 2023).

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Representative model, for educational purposes only.

Frontal lobe highlighted on the Durgical 3D model