What is ADHD?

ADHD is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that is more pronounced than would be expected for a person's age and developmental stage, and that causes meaningful difficulty in day-to-day life.

To meet the diagnostic criteria, several symptoms must have been present before the age of 12, must show up across at least two different settings (such as home and school, or work and relationships), and must not be better explained by another condition. There is no blood test or brain scan that diagnoses ADHD—it is assessed through careful observation of behavior across contexts, often with input from parents, teachers, or partners.

The three presentations

Combined presentation (F90.2)

Both inattention and hyperactivity-impulsivity symptoms are present at the required level. This is the most commonly diagnosed presentation.

Predominantly inattentive presentation (F90.0)

The inattention criteria are met but hyperactivity-impulsivity criteria are not. This presentation is often overlooked—especially in girls—because it is less disruptive outwardly, but the internal struggle with focus, organization, and follow-through can be just as impairing.

Predominantly hyperactive-impulsive presentation (F90.1)

The hyperactivity-impulsivity criteria are met but inattention criteria are not. This presentation is more common in younger children and tends to become less prominent with age.

Inattention symptoms

Children up to age 16 need six or more of these symptoms; adolescents aged 17 and older and adults need five or more, present for at least six months:

Makes careless mistakes—difficulty paying close attention to details in schoolwork, work tasks, or other activities
Difficulty sustaining attention—trouble keeping focus during tasks, lectures, or conversations
Seems not to listen—appears to be elsewhere even when spoken to directly, with no obvious distraction
Doesn't follow through—starts tasks but loses focus and gets sidetracked; fails to finish schoolwork, chores, or duties
Poor organization—difficulty managing tasks and activities, keeping materials orderly, managing time, and meeting deadlines
Avoids sustained mental effort—reluctant to engage with tasks that require prolonged concentration, such as completing reports or lengthy reading
Loses things—frequently misplaces items needed for tasks, such as keys, phone, wallet, or paperwork
Easily distracted—attention is pulled away by unrelated thoughts or external stimuli
Forgetful—frequently forgets daily tasks such as chores, errands, returning calls, or keeping appointments

Hyperactivity and impulsivity symptoms

The same thresholds apply—six or more for children, five or more for adolescents and adults, for at least six months:

Fidgets—taps hands or feet, squirms in seat
Leaves seat—gets up when expected to remain seated
Runs or climbs inappropriately—in adults, this may appear as an internal sense of restlessness rather than physical movement
Unable to play quietly—difficulty engaging in leisure activities without making noise
"On the go"—acts as if driven by a motor; uncomfortable being still for extended periods
Talks excessively—difficulty moderating the amount of talking in social situations
Blurts out answers—answers before a question is finished; finishes others' sentences; difficulty waiting to respond in conversation
Difficulty waiting a turn—in queues, games, or conversation
Interrupts or intrudes—butts into conversations, games, or activities; uses others' things without asking

How common is it?

~7.2%

of children worldwide are affected

~2.5%

of adults worldwide are affected

2:1

ratio of males to females diagnosed in children

ADHD is more commonly diagnosed in males, though the gap narrows in adulthood (approximately 1.6:1). Girls and women are more likely to have the inattentive presentation, which is often missed or misattributed to anxiety or low ability. Many women receive a first diagnosis of ADHD in adulthood after years of struggling without support.

When does it start and how does it progress?

ADHD is most often identified during the early school years, when demands for sustained attention, sitting still, and following instructions become more prominent. However, some children—particularly those with the inattentive presentation or high intelligence—may not be identified until later in school, or even in adulthood.

Hyperactivity tends to decrease with age and may look quite different in adults—appearing as restlessness, difficulty relaxing, or a tendency to take on too many things at once. Inattention and impulsivity often persist into adulthood, continuing to affect work, relationships, and daily management of life. Many adults are surprised to receive an ADHD diagnosis after a lifetime of struggling in ways they couldn't fully explain.

Risk factors

Genetics

ADHD is highly heritable—around 74% of the risk is estimated to be genetic, making it one of the most heritable psychiatric conditions. No single gene is responsible; instead, many genes each contribute a small amount. Having a parent or sibling with ADHD substantially increases the likelihood of the condition.

Prenatal and early environment

Premature birth, low birth weight, and exposure to tobacco smoke during pregnancy are associated with increased risk. These factors may affect brain development in ways that increase vulnerability to ADHD.

Temperament

Children who show reduced behavioral inhibition and a strong drive toward novelty and stimulation from an early age may be at higher risk. These traits are likely related to the underlying neurobiology of ADHD.

ADHD and suicidal thoughts

ADHD is associated with an increased risk of suicidal thoughts and attempts, particularly when co-occurring conditions such as depression, conduct disorder, or substance use disorders are also present. If you or someone you know is struggling, please reach out for help.

988 Suicide & Crisis Lifeline: Call or text 988 (available 24/7 in the U.S.)

Conditions that often occur alongside ADHD

ADHD frequently co-occurs with other conditions, which can complicate diagnosis and require their own treatment:

Oppositional defiant disorder and conduct disorder
Anxiety disorders
Depressive disorders
Obsessive-compulsive disorder (OCD)
Autism spectrum disorder
Learning disorders (such as dyslexia)
Sleep disorders
Substance use disorders

What to do next

ADHD is well understood and responds well to treatment. The most effective approaches combine medication and behavioral support. Stimulant medications—such as methylphenidate and amphetamine-based treatments—are highly effective for most people and are among the most studied medications in psychiatry. Non-stimulant options are available for those who don't respond well or prefer to avoid stimulants.

Alongside medication, cognitive behavioral therapy (CBT) adapted for ADHD can help with organization, time management, and managing the emotional aspects of the condition. For children, parent training and school-based accommodations play an important role. For adults, coaching, structured routines, and workplace adjustments can make a significant difference.

If you think you or your child might have ADHD, speaking with a GP or psychiatrist is a good starting point. A formal assessment will look at symptoms across settings and help determine the best path forward.