What ADHD Is (and Isn't)
ADHD (Attention Deficit Hyperactivity Disorder) is a neurodevelopmental condition affecting how the brain regulates attention, activity, and impulses. It's not about being naughty, lazy, or badly parented - it's about brain differences.
According to the DSM-5-TR (the diagnostic manual used internationally), ADHD is characterised by a persistent pattern of inattention and/or hyperactivity-impulsivity that:
- Interferes with functioning or development
- Was present before age 12 (even if not diagnosed until later)
- Is present in two or more settings (e.g., home and school)
- Is not better explained by another condition
- A neurodevelopmental condition present from early childhood
- A difference in brain development affecting self-regulation
- Highly heritable (approximately 74% genetic component)
- Associated with differences in dopamine and noradrenaline pathways
- Characterised by difficulties with attention, impulsivity, and/or hyperactivity
- A spectrum - severity and presentation vary widely
- Treatable with environmental support, behavioural strategies, and sometimes medication
- Often co-occurring with other conditions (anxiety, autism, learning difficulties)
- Caused by poor parenting, too much screen time, or sugar
- A lack of willpower, laziness, or bad behaviour
- Something children "grow out of" (though presentation changes with age)
- A modern invention or overdiagnosed (rates are consistent globally)
- Just about hyperactivity (inattentive presentations are common)
- A male condition (girls are frequently underdiagnosed)
- An excuse for bad behaviour
- A barrier to success (many people with ADHD thrive with the right support)
What the research tells us
ADHD affects approximately 5-7% of children worldwide
Meta-analyses of prevalence studies (Polanczyk et al., 2015)
Heritability is approximately 74%, making it one of the most heritable psychiatric conditions
Twin and family studies (Faraone & Larsson, 2019)
Brain imaging shows differences in frontal regions, basal ganglia, and cerebellum
Neuroimaging meta-analyses (Hoogman et al., 2017)
ADHD persists into adulthood in approximately 50-65% of cases
Longitudinal studies (Faraone et al., 2021)
Co-occurrence with other conditions is the rule rather than the exception
Clinical guidelines (NICE NG87, AAP 2019)
Brain differences in ADHD
Brain imaging studies have identified consistent differences in people with ADHD. These are subtle differences in size and function - not damage or defects.
Slightly smaller volume; matures approximately 2-3 years later
Reduced volume in caudate and putamen regions
Reduced volume, particularly in posterior regions
Less efficient dopamine transmission and reuptake
The term "Attention Deficit" is somewhat misleading. People with ADHD don't have less attention - they have difficulty regulating attention.
This is why someone with ADHD can focus intensely on interesting activities (sometimes called "hyperfocus") while struggling with tasks they find boring or unrewarding. The challenge isn't attention itself - it's the ability to direct attention voluntarily, especially when motivation is low.
Many researchers and advocates prefer terms like "attention regulation difficulty" or emphasise that ADHD involves differences in executive function more broadly.
The neuroscience in brief
Dopamine and noradrenaline are neurotransmitters (chemical messengers) that play key roles in attention, motivation, and executive function. In ADHD, these systems work less efficiently.
Dopamine is involved in reward processing and motivation. Lower dopamine activity can make it harder to sustain effort on tasks that aren't immediately rewarding - even when you know they're important.
Noradrenaline helps with alertness and filtering out distractions. When noradrenaline signalling is less efficient, it's harder to maintain focus and ignore irrelevant information.
This is why ADHD medications (both stimulants and non-stimulants) work by increasing the availability of these neurotransmitters in the brain.