Theo is 7 and his teacher has already sent three notes home: he will not stay in his seat, he answers before the question is finished, he knocks his chair over every morning. In the same classroom, Livia is no trouble at all. She looks at the board, smiles when her name is called, and at the end of the term nobody understands why the test came back blank where she "knew it all".
Both of them have ADHD. The difference between them is not one of severity but of presentation: in one, the body that will not stop takes over; in the other, attention keeps slipping away. The loudest type is not the most severe, and the quietest is not the mildest.
What are the types of ADHD?
There are three, defined in the DSM-5-TR by counting symptoms in two groups. If the person reaches the threshold only in the inattention group, the presentation is predominantly inattentive; only in the hyperactivity-impulsivity group, predominantly hyperactive-impulsive; in both, combined. The threshold is six symptoms up to age 16 and five from 17 on, for at least six months.
The manual lists nine symptoms in each group (the full list is in what is ADHD). In the WHO's ICD-11, each presentation has its own code: 6A05.0 (inattentive), 6A05.1 (hyperactive-impulsive) and 6A05.2 (combined).
Predominantly inattentive
Key symptoms: loses the thread, forgets appointments, loses things, avoids long tasks, seems not to listen. At school and at work: low grades "for no reason", late work despite real effort, emails read and never answered. Most common in: girls, women and adults. The one that most often goes unnoticed.
Predominantly hyperactive-impulsive
Key symptoms: cannot sit still, talks too much, interrupts, answers before the question ends, cannot wait their turn. At school and at work: notes from the teacher, told off for "misbehaving"; in adults, impulsive decisions and restlessness on the inside. Most common in: young children, especially boys. Leads to earlier diagnosis, because it bothers people.
Combined
Key symptoms: reaches the threshold in both groups; inattention and impulsivity add up. At school and at work: the student who disrupts the class and does not finish the homework; the adult who starts ten projects and delivers none. Most common in: school-age children. The most frequent and the most studied.
| Inattentive | Hyperactive-impulsive | Combined | |
|---|---|---|---|
| Symptoms | ≥6 (≥5 in adults) of inattention; fewer of hyperactivity | ≥6 (≥5 in adults) of hyperactivity-impulsivity; fewer of inattention | ≥6 (≥5 in adults) in each group |
| Typical age at diagnosis | Late: adolescence or adulthood, when the demand for organization grows | Early: preschool and the first school years | School age, prompted by complaints from the school |
| How it shows up day to day | Bill paid late with money sitting in the account, meeting heard but not retained, keys lost | Foot tapping, talking over people, impulse buys, "I can't relax" | Starts a lot, finishes little, and interrupts on top of it |
| Most common in | Girls, women and adults | Young children, mostly boys | School-age children |
| Risk of going unnoticed | High: bothers no one but the person themselves | Low: it is visible, though mistaken for "lack of discipline" | Medium: the behavior gets noticed; the inattention gets labeled "laziness" |
So which type is the most common? It depends on who you look at. In school-age children, the combined presentation: ABDA, the Brazilian ADHD association, cites around 66% combined, 26% inattentive and 8% hyperactive-impulsive. In girls and women, the inattentive presentation, according to the consensus statement by Young and colleagues (2020) and the review by Quinn and Madhoo (2014). In adults, visible hyperactivity has already faded and inattention is what is mostly left.
Predominantly inattentive ADHD: the type nobody sees
This is the presentation in which the person meets the criteria for inattention (six or more symptoms, five from age 17) but not for hyperactivity-impulsivity. The impairment is in sustaining attention, organizing, remembering and finishing. Because it bothers no one, it is the one that takes longest to diagnose.
Carla, 34, an analyst. She walks into the meeting determined to pay attention, and she does: she looks at whoever is speaking, nods, takes notes. When she walks out, she does not know what was decided. The client's email, she has opened six times today and still has not answered. The car keys are where she "would never leave them".
From the outside, Carla looks distracted. From the inside, she works harder than her colleagues to deliver the same thing, and the exhaustion of that is invisible. It is the pattern the Young consensus describes in girls with ADHD: socially adapted behavior and extra effort that mask the impairment until it no longer fits inside a life. The article on ADHD in women goes deeper into this.
Inattentive does not mean mild. It means quiet.
Predominantly hyperactive-impulsive ADHD: "driven by a motor"
This is the presentation in which the threshold is reached in the hyperactivity-impulsivity group and not in the inattention group. The symptoms are about movement and brakes: cannot sit still, talks too much, interrupts, answers before the question ends, cannot wait their turn. It is the most visible of the three and the rarest, especially after childhood.
Theo, the boy from the opening, is the classic version. But the DSM's wording for one of the symptoms, acting "as if driven by a motor", applies to adults too. Rafael, 29, does not run around the room. He bounces his foot under the table for the entire meeting, finishes other people's sentences, hits send before rereading, and at night his head is still in third gear. The ASRS, the screening questionnaire for adults, asks exactly this: whether you feel "overly active and compelled to do things, like you were driven by a motor".
The engine that never switches off
Picture a car stopped at a red light with the engine revving the whole time. It goes nowhere, but it vibrates, it makes noise, and the lightest touch on the pedal leaves tire marks. In a child, the car actually moves: runs, climbs, knocks things over. In an adult, the car has learned to stay put, but the engine never switched off. That is why adult hyperactivity shows up as restlessness on the inside, fast talking, impatience and decisions made before thinking.
Impulsivity is the most expensive part of this presentation in adult life, because it moves from the body into decisions: the resignation handed in while angry, the purchase that did not fit the budget. The 2021 international consensus records a 23% higher risk of car accidents and a 40 to 50% higher risk of accidental injury in ADHD.
Combined ADHD: when both groups show up together
This is the presentation in which the person reaches the threshold in both symptom groups at the same time. It is the most frequent in school-age children, the most studied and, because it adds up both kinds of impairment, usually the most obvious to the school and the family.
Lucas is 14. In class, he is Theo grown up: chats, gets up four times to sharpen his pencil, answers without being called on. But his report card tells Livia's story: assignments half done, tests with the last page blank, notes in his backpack that never made it home. The school complains about the behavior, the parents worry about the grades, and both are looking at the same disorder from different sides.
Compensating is harder here: someone who is only inattentive learns early to use a planner; someone who is combined has the planner and the impulsivity to ignore it.
Can your type of ADHD change over time?
Yes, and often. The DSM-IV called the three forms "subtypes"; the DSM-5 switched to "presentations" because the classification is not stable: the same person can be combined at 8 and inattentive at 25.
The most common path is a single one: motor hyperactivity decreases with age (the Brazilian Society of Pediatrics records this in its 2025 document) and inattention stays. The meta-analysis by Faraone, Biederman and Mick (2006) showed that, at 25, only about 15% of children still meet the full criteria, but about 65% keep symptoms with some impairment. The full picture disappears in many people; what remains is almost always the inattentive part.
At 8
Runs around the room, talks nonstop, does not finish homework. The school notices, the parents are called in, the diagnosis comes: combined presentation. What bothers people is the behavior; the inattention stays in the background.
At 30
Sits quietly in the meeting but retains nothing. Misses deadlines, forgets the bill, starts projects and abandons them. The hyperactivity has turned into restlessness on the inside. Assessed today for the first time, the presentation would be inattentive.
The MTA study, published by Sibley and colleagues in 2022, followed 558 children for 16 years. In 63.8% of cases the ADHD fluctuated: periods of remission alternating with the return of symptoms, depending on the stage of life. Only 9.1% had sustained remission. The type written on the report is a snapshot of the last six months, not a destiny. And for those who "stopped having ADHD" in adolescence, what often stopped was the hyperactivity; the inattention carried on, with nobody looking.
15%
65%
63.8%
9.1%
Does ADD exist? The old term for ADHD without hyperactivity
"ADD" (attention deficit disorder) is the old name for ADHD without hyperactivity. Today, the correct name is ADHD, predominantly inattentive presentation. It is the same disorder, with the same criteria for duration, onset before age 12 and impairment in more than one setting.
The name comes from earlier editions of the American manual. The DSM-III, in 1980, used "attention deficit disorder" with and without hyperactivity. The acronym stuck in everyday English and never left; in Brazil, the equivalents "TDA" and "DDA" are still in circulation too. The editions that followed unified everything under "ADHD", and the DSM-IV, in 1994, created the three subtypes that the DSM-5 turned into presentations.
Someone who says "I have ADD" is describing the inattentive presentation. The problem is what the acronym carries with it: the idea that, without the "H", the condition is smaller.
Mild, moderate or severe ADHD: what changes?
Beyond the presentation, the DSM-5-TR asks the clinician to rate current severity as mild, moderate or severe. The criterion is twofold: how many symptoms exist beyond the minimum needed for the diagnosis, and how much they get in the way of life. Severity is independent of type and can change from one assessment to the next.
The manual's wording defines it like this. Mild: "few, if any, symptoms in excess of those required to make the diagnosis are present", with minor impairment. Moderate: "symptoms or functional impairment between 'mild' and 'severe'". Severe: "many symptoms in excess of those required", or several symptoms that are particularly severe, or marked impairment.
The yardstick is the same for all three presentations. Nine symptoms of inattention, zero of hyperactivity and one job lost per year is severe inattentive ADHD. Six symptoms of hyperactivity in a boy who is doing fine at school is mild hyperactive-impulsive ADHD. The type says where the problem is; the severity says how big it is. Both go into the report and guide treatment, which the UK's NICE guideline recommends starting with changes to the environment before considering medication.
How do I find out which type of ADHD I have?
Only through a clinical assessment. No exam or online test defines the presentation: what defines it is the interview with a physician (a psychiatrist, neurologist or pediatric neurologist; in some countries a clinical psychologist can also diagnose), who counts the symptoms from each group present for at least six months, confirms onset before age 12 and impairment in more than one setting.
- Do an honest screening. The ADHD test uses the ASRS-18, the WHO questionnaire for adults, which separates questions about inattention from questions about hyperactivity-impulsivity. It is a starting point, not a diagnosis.
- Gather the history. Old report cards, accounts from parents or siblings. The presentation depends on the last six months, but the diagnosis requires symptoms before age 12.
- Take it to the appointment. The clinician counts the symptoms in each group, rates presentation and severity, and rules out what mimics ADHD: anxiety, depression, poor sleep, hypothyroidism.
- Ask for both labels. Presentation and severity. Both change over time, and a reassessment a few years from now may come out differently.
And after the diagnosis? The type tells you where to concentrate the structure. For the inattentive presentation, Barkley recommends externalizing: taking what needs to be remembered out of your head and putting it in the environment, in the place and at the time it will be used. For the hyperactive-impulsive presentation, scheduled movement breaks, as NICE suggests, and a forced pause between the impulse and the action. For the combined presentation, both. The articles on executive function and time blindness explain why this works.
The gap that remains
Everything the previous section recommends has the same weak point, and it is biggest in exactly the inattentive presentation: it depends on something bringing the information back at the moment it matters. Writing things down, Carla does. What fails is the next part, where something has to call her at 3 p.m. and insist when she has, once again, forgotten to look.
That is what made me build ASB. Sofia, the assistant, lives on WhatsApp: you send a voice note on the way home, she turns it into a task with a deadline, and at the right time she calls, and insists, at whatever level you choose, until the thing is done. The type changes over time. The need for something to bring the information back does not.