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Guide · ADHD

What is ADHD, and how is it diagnosed in Australia?

ADHD stands for attention deficit hyperactivity disorder. It is a neurodevelopmental condition, meaning it comes from differences in how the brain develops, and it affects attention, activity levels and impulse control. Here is what it is, how common it is, what causes it, and how diagnosis and treatment work in Australia.

Updated 5 October 2026 · About 11 minutes to read · All guides

In short

  • ADHD stands for attention deficit hyperactivity disorder: a neurodevelopmental condition in which inattention, hyperactivity or impulsivity are persistent, start in childhood and get in the way of daily life.
  • It has two symptom groups, inattention and hyperactivity-impulsivity, and three presentations: predominantly inattentive, predominantly hyperactive-impulsive, and combined.
  • Worldwide, about 5% to 7% of children and about 2.5% of adults have ADHD. Australia's national child survey found 7.4% of 4 to 17 year olds met criteria.
  • ADHD is strongly genetic: across 37 twin studies, about 74% of the variation in ADHD traits was inherited. Sugar, screens and parenting have not been shown to cause it.
  • In Australia, ADHD is diagnosed by paediatricians, psychiatrists and psychologists, working to the 2022 national guideline; treatment usually combines medication with psychological support.

What ADHD is

ADHD stands for attention deficit hyperactivity disorder. In plain words, it is a condition where a person finds it much harder than most people their age to hold attention, sit with boredom, organise themselves, or stop and think before acting. Everyone has moments like that; in ADHD they are frequent, long-standing and get in the way of school, work or relationships.

Formally, ADHD is a neurodevelopmental condition: Healthdirect describes it as a brain development condition that begins in early childhood.

The formal definition

Clinicians diagnose ADHD against one of two manuals: the DSM-5-TR, the American Psychiatric Association's manual, or the World Health Organization's ICD-11, where ADHD has the code 6A05. As summarised by the APA and the US Centers for Disease Control and Prevention, the DSM criteria require:

  1. at least six symptoms of inattention and/or six of hyperactivity-impulsivity for children up to 16, or five for people aged 17 and over, lasting at least six months
  2. several symptoms present before age 12
  3. symptoms in two or more settings, such as home and school
  4. clear evidence that the symptoms interfere with social, school or work life
  5. symptoms not better explained by another condition

So ADHD is defined by impact, not traits alone, and because symptoms must date from childhood, an adult assessment still looks back at the school years (see ADHD in adults).

The two symptom groups, and the three types of ADHD

ADHD symptoms fall into two groups. Inattention is about focus, organisation and follow-through. Hyperactivity-impulsivity is about restlessness and acting before thinking. They look different in a seven year old and a 37 year old.

Symptom groupIn childrenIn adults
InattentionNot finishing tasks, easily distracted, not seeming to listen, trouble remembering and organising, losing things, avoiding anything that needs sustained effortTrouble managing time and staying organised, running late, procrastinating, difficulty following conversations, mind-wandering
Hyperactivity-impulsivityFidgeting and squirming, leaving their seat, running or climbing at the wrong times, talking non-stop, blurting out answers, trouble waiting, interruptingFeeling restless and unable to relax, talking excessively or interrupting, excessive spending, risk-taking, reacting quickly without thinking

In adults, the APA notes, hyperactivity and impulsivity may fade or become extreme restlessness, while inattention tends to persist.

The three presentations

Depending on which group dominates, ADHD has one of three presentations, the manual's word for types:

  • Predominantly inattentive: enough inattention symptoms, but not enough hyperactive-impulsive ones. This is what most people mean by "ADD".
  • Predominantly hyperactive-impulsive: the reverse.
  • Combined: enough symptoms in both groups.

A 2012 meta-analysis of 86 studies found the inattentive presentation is the most common in the general population, while the combined presentation is more often referred to clinics. See ADD vs ADHD on whether "ADD" still exists, and ADHD in women and girls on why inattentive symptoms get missed.

How common is ADHD?

Estimates move with the criteria and methods used, but the large reviews agree:

  • A 2012 meta-analysis of 86 studies (163,688 children and adolescents) found 5.9% to 7.1% whether ADHD was rated by parents, teachers or clinicians.
  • The World Federation of ADHD's 2021 international consensus statement puts it at 5.9% of young people and 2.5% of adults, at similar rates across continents.

ADHD in Australia

The main Australian source is Young Minds Matter, the second national child and adolescent mental health survey, which interviewed the parents or carers of 6,310 children aged 4 to 17 in 2013–14. It found that 7.4% had ADHD in the previous 12 months, the most common mental disorder in that age group, ahead of anxiety disorders at 6.9%. The Australian Institute of Health and Welfare reports 8.2% among 4 to 11 year olds, and 11% among boys of that age. Healthdirect's rounder figure is about 1 in 20 Australians. Treatment is rising: PBS prescriptions for ADHD medicines grew just under 18% a year on average from 2013–14, and adults were half of new patients in 2022–23.

Adults

A 2021 global meta-analysis of 40 studies from 30 countries estimated that 2.58% of adults have persistent ADHD, meaning it began in childhood, and 6.76% have symptomatic adult ADHD when childhood onset is not required; both fell with age. No Australian study has measured adult ADHD with current criteria; the national guideline expects 2% to 6%.

What causes ADHD?

Nobody chooses ADHD, and nobody causes it in their child. It is mostly inherited, brain development follows a somewhat different timetable, and a few early-life factors add risk.

Genes

A 2019 review in Molecular Psychiatry found that across 37 twin studies, the average heritability of ADHD and of inattention and hyperactivity traits was 74%: about three quarters of the variation between people traces back to genes. There is no single ADHD gene; about a third of that heritability comes from many common variants with tiny individual effects, plus some rare deletions and insertions of DNA.

Brain development

The largest brain imaging study so far pooled MRI scans of 1,713 people with ADHD and 1,529 without, aged 4 to 63, and found slightly smaller volumes in several deep brain structures involved in reward, emotion, memory and movement. The differences were small, most marked in children and faded in adults, which fits the idea that brain maturation in ADHD is delayed rather than permanently different. They are group averages: the consensus statement says they cannot be used to diagnose ADHD, so a brain scan cannot tell you whether you or your child has it.

Pregnancy and birth

The Australian guideline lists early-life factors linked with higher rates of ADHD: prenatal exposure to lead, maternal smoking and the epilepsy medicine valproate, very preterm birth (before 32 weeks), low birth weight, and psychosocial adversity. The consensus statement reports about three times the rate of ADHD in very preterm or very low-birth-weight babies, and around four times the odds with higher blood lead. Many of these links shrink or disappear once family history is taken into account (the smoking link disappears after adjusting for ADHD in the family), so the statement calls them correlates, not causes.

What does not cause ADHD

  • Sugar. A meta-analysis of 23 controlled studies in JAMA found that sugar does not affect children's behaviour or thinking, though a small effect in some children could not be ruled out.
  • Screens. A 2014 meta-analysis of 45 studies found only a small statistical link between media use and ADHD-type behaviours (a correlation of 0.12), and such studies cannot show which way the link runs; restless, distractible children may simply use screens more.
  • Parenting. The ADHD Evidence Project, which curates the research behind the consensus statement, lists "poor parenting" among the myths: many parents of children with ADHD have ordinary parenting skills, and parenting programs, while helpful, do not make ADHD go away. Family stress can make symptoms harder to live with; that is different from causing them.

Conditions that often come with ADHD

ADHD rarely travels alone. Australia's guideline says around two-thirds of children with ADHD have a co-occurring mental health or developmental condition, most often oppositional defiant disorder (a persistent pattern of angry, defiant behaviour), anxiety, learning disorders, autism and tics. In a Danish study of 14,825 children and teenagers diagnosed in hospital clinics, 52% had at least one other psychiatric diagnosis: conduct and oppositional disorders (16.5%), developmental disorders of language, learning or movement (15.4%), autism (12.4%) and intellectual disability (7.9%) were the most frequent. Clinic samples pick up more complex cases, so community rates are likely lower.

Healthdirect adds anxiety, depression, learning difficulties and obstructive sleep apnoea (the airway being blocked during sleep). For adults the guideline's figure is up to 80%; see ADHD in adults.

A good assessment looks for these conditions because they change what support is needed, and because anxiety, sleep problems and learning difficulties can look like ADHD on their own. When autism and ADHD both fit, see what AuDHD means.

How ADHD is diagnosed and treated in Australia

Who can diagnose ADHD

Healthdirect lists paediatricians, psychiatrists and psychologists as the professionals who diagnose ADHD, and your GP can refer you. Some GPs with extra training can also diagnose and, in NSW, start medication. Rules differ by state and are changing; see our ADHD assessment page.

What an assessment should include

Since 2022 Australia has had its own guideline, the Australian Evidence-Based Clinical Practice Guideline for ADHD, from the Australasian ADHD Professionals Association (AADPA). It says the assessment should include a full clinical and psychosocial assessment, a developmental, mental health and medical history, reports from other people, and a medical check to exclude other causes, and that the clinician must confirm the symptoms meet the criteria, cause significant impairment and occur in two or more settings.

Questionnaires are part of this, not the whole of it. The most used adult screener, the World Health Organization's Adult ADHD Self-Report Scale (ASRS), has a six-question short form that in a US national survey identified about 69% of adults with ADHD and correctly cleared 99.5% of those without. A positive screen is a reason to look further, not a diagnosis. Our free ADHD test uses those six questions (the ASRS guide explains the scoring); for children, see ADHD in children.

How ADHD is treated

The guideline recommends multimodal treatment: medication and non-medication supports together. For children it recommends parent and family training, and for adolescents cognitive behavioural therapy (CBT); Healthdirect lists CBT for adults too.

On medication, the guideline recommends a stimulant (methylphenidate, dexamfetamine or lisdexamfetamine) first, with the non-stimulants atomoxetine or guanfacine when stimulants are unsuitable or do not work, and caution in children under five. The main evidence is a 2018 network meta-analysis in The Lancet Psychiatry of 133 double-blind randomised trials in 14,346 children and adolescents and 10,296 adults. At around 12 weeks, on clinicians' ratings every medicine studied beat placebo in children and most did in adults, though long-term evidence is lacking. In Australia the stimulants are Schedule 8 controlled medicines, prescribed only by doctors with special approval under state and territory rules, and the main ADHD medicines are subsidised on the PBS. Our ADHD medication guide covers each medicine, its side effects and the rules.

ADHD and neurodivergence

Alongside the medical definition, many people describe ADHD as a form of neurodivergence: a brain that works differently from the majority, with real difficulties in some settings and real strengths in others. The Raising Children Network uses similar language, calling ADHD a natural variation in the way the brain processes information. The two framings are not in conflict: the diagnosis exists because the difficulties are real and naming them opens the door to treatment and adjustments, and the neurodivergence framing is a reminder that the person is not broken. See what neurodivergent means and is ADHD a disability?

The free screener is a reasonable first step. It cannot diagnose anyone, and an assessment can conclude ADHD, not ADHD, or something else.

Questions people ask

What does ADHD stand for?

ADHD stands for attention deficit hyperactivity disorder. It is a neurodevelopmental condition, diagnosed when inattention and/or hyperactivity-impulsivity are persistent, began in childhood and interfere with daily life. The older label ADD is not used in the current manuals; what it described is now the predominantly inattentive presentation.

What are the 3 types of ADHD?

The DSM-5-TR describes three presentations: predominantly inattentive, predominantly hyperactive-impulsive, and combined, with enough symptoms in both groups. A 2012 meta-analysis found the inattentive presentation is the most common in the general population, while the combined presentation is more often seen in clinics.

What are the main symptoms of ADHD?

Inattention symptoms include being easily distracted, not finishing tasks, losing things and avoiding anything that needs sustained effort. Hyperactive-impulsive symptoms include fidgeting, talking non-stop, blurting out answers, trouble waiting and interrupting. Children need six symptoms from a group and people aged 17 and over need five, with several present before age 12 and in two or more settings.

Is ADHD a mental illness or a disability?

Both the DSM-5-TR and the ICD-11 classify ADHD as a neurodevelopmental disorder, alongside autism and learning disorders. Whether it counts as a disability depends on the setting and how much it affects the person, and it does not appear on the NDIS access lists on its own. See is ADHD a disability?

Is ADHD genetic?

Largely, yes. Across 37 twin studies the average heritability of ADHD and ADHD traits was 74%, and Australia's ADHD guideline gives 70% to 80%. There is no single ADHD gene; many common variants with tiny effects add up, and genes raise the odds rather than deciding the outcome.

Can adults have ADHD?

Yes. Many adults are first diagnosed well into adult life. A 2021 global meta-analysis estimated that 2.58% of adults have ADHD that began in childhood and 6.76% have adult ADHD symptoms when childhood onset is not required. Adults need five symptoms from a group rather than six. See ADHD in adults.

Wondering whether an assessment makes sense? The free screener takes about three minutes, for your child, your adult son or daughter, or yourself. It suggests which assessment fits, and it will tell you if one does not look like the right next step. Start the free screener.

Related

ADHD in adults · ADD vs ADHD · ADHD in children · Free ADHD test · ADHD assessment · All guides

Where this information comes from

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Links to external sites are provided for reference. We do not control them and they may change. Last checked 5 October 2026.

This guide is general information, not medical advice. If you are worried about yourself or your child, talk to your GP.

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