New to ADHD ?

A simple guide explaining what ADHD is, and how it can show up in adults and children. Autism overview is coming soon!

What is ADHD?

ADHD (Attention Deficit Hyperactivity Disorder) is a neurodevelopmental condition affecting how the brain regulates attention, impulse control, and activity levels. It is recognised in both children and adults, and it is one of the most common and well-researched neurodevelopmental conditions in the world.

ADHD is not a character flaw, a parenting failure, or a lack of effort. It reflects genuine differences in how the brain develops and functions, particularly in areas involved in executive function, working memory, and emotional regulation.

The condition is described in two major diagnostic frameworks: the DSM-5 (Diagnostic and Statistical Manual, used widely in psychiatry) and the ICD-11 (International Classification of Diseases, published by the WHO). Both recognise ADHD as a legitimate neurodevelopmental diagnosis.

The three presentations

DSM-5 describes three presentations of ADHD:

Predominantly inattentive: difficulty sustaining attention, following through on tasks, organising, and keeping track of things. Often described as "daydreamy." Historically under diagnosed, particularly in girls.

Predominantly hyperactive-impulsive: restlessness, difficulty sitting still, acting or speaking without thinking, interrupting. More likely to be noticed in childhood.

Combined presentation: meeting criteria for both inattentive and hyperactive-impulsive symptoms. The most common presentation in clinical populations.

Presentations can change across a person's life. Someone diagnosed with hyperactive-impulsive ADHD in childhood may present more inattentively as an adult.

How ADHD shows up in adults

In adults, ADHD often looks quite different from the textbook picture of a restless child. Common experiences include:

  • Time blindness: difficulty sensing how much time has passed or how long tasks will take
  • Executive dysfunction: struggling to start tasks, switch between them, or hold multiple steps in mind at once
  • Emotional dysregulation: feelings that arrive suddenly and at full intensity, often described as rejection sensitive dysphoria (RSD)
  • Hyperfocus: the ability to become intensely absorbed in things that hold interest, sometimes to the exclusion of everything else
  • Chronic underachievement: a persistent sense of not reaching your potential despite obvious capability
  • Disorganisation: losing things, missing appointments, struggling with routines

Many adults reach diagnosis only after years of being told they were lazy, careless, or "not trying hard enough." This is particularly common for women and people who were high-achieving students, where compensation strategies masked the condition for years and the cognitive energy exerted into maintaining the social facade can cause burn out in work, education, at home and in relationships etc.

How ADHD shows up in children

In children, ADHD is more commonly recognised, though girls and quieter children are still frequently missed. Signs vary by age.

In younger children, hyperactivity and impulsivity are often more visible: difficulty waiting, interrupting, physical restlessness. In older children and teenagers, inattentiveness, disorganisation, and emotional difficulties may be more prominent.

A child who is quiet, compliant, and struggles to follow instructions or finish work may have inattentive ADHD that goes unrecognised for years.

ADHD and autism

ADHD and autism frequently co-occur. Research suggests that around 50-70% of autistic people also meet criteria for ADHD, and a significant proportion of people with ADHD also have autistic traits. The two conditions share some features but are distinct, and being assessed for one does not rule out the other.

If you or your child has received one diagnosis and you feel something else is being missed, it is reasonable to raise this with your GP or assessing clinician.

The neurodiversity community has coined the termed “AuDHD", which while not a formal clinical diagnosis in itself and a shortened way of saying a person has both ADHD and autism, it captures the lived reality of navigating the world with the combined traits, strengths, and challenges of both conditions. Living with both can present a constant internal duality, a push and pull between seemingly contradictory needs and ways of processing the world.

Trusted further reading

ADHD Scot is an independent, non-clinical information project. Nothing here is medical advice. If you think you or your child may have ADHD, the right first step is a conversation with your GP.

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