It is common to hear that neurodivergent people “think differently” or that their brains are “wired differently”. Both phrases can be trying to name something real. Many autistic people, people with ADHD, dyslexia, dyspraxia or Tourette syndrome recognise enduring differences in attention, sensory experience, movement, language, learning, energy, motivation or social communication. Yet the neuroscience is more interesting, and more cautious, than the usual shorthand suggests.
Research supports the view that several neurodevelopmental profiles are associated with differences in brain development and information processing. It does not support the idea that there is one identifiable neurodivergent brain, set cleanly apart from one uniform neurotypical brain. Nor does it show that difference is the same thing as damage, deficit or incapacity.
What does “neurodivergent” mean in research?
Neurodivergent is a useful umbrella term in everyday and community language, but it is not a single scientific diagnosis. Autism, ADHD, dyslexia, developmental coordination disorder and Tourette syndrome involve partly distinct developmental pathways. They can also overlap in the same person.
“Neurotypical” is not a single biological category either. Brains vary enormously across all people. Age, sleep, stress, trauma, health, medication, education, language, culture and relationships all affect what a person can do on a particular day and how their nervous system responds.
This matters because a group average is not a description of any individual. A study may find an average difference between thousands of autistic and non-autistic participants, while the two groups still overlap substantially. A scan cannot tell a clinician whether a particular person is autistic or has ADHD, and it should not be used as a shortcut around careful listening, developmental history and the person’s own account of their life.
What brain research has found
Large MRI studies have found small average differences in the size or developmental trajectory of some brain structures in ADHD. One international study of more than 3,000 participants found that, on average, several subcortical structures were slightly smaller in people with ADHD, particularly in childhood. These included areas involved in motivation, learning, emotion and movement. The effects were small and were less clear in adults, which suggests developmental variation rather than a fixed and uniform “ADHD brain”.
Research on autism has also found differences in brain structure and connectivity. These may involve sensory processing, perceptual integration, language, social attention and the way that large-scale brain networks coordinate. But the findings vary markedly between studies and between people. Some differences appear at one stage of development and not another. Some are affected by co-occurring anxiety, ADHD, intellectual disability, sleep difficulties or medication. Sex and gender have also been under-represented or handled poorly in much earlier research.
The most reliable conclusion is not that one region is universally larger, smaller, over-connected or under-connected. It is that autistic neurobiology is heterogeneous: there are multiple patterns, with some areas of convergence. A 2024 review spanning seven neuroimaging methods reached precisely this kind of conclusion.
Functioning differently is not the same as functioning badly
When someone says that their brain functions differently, they may be referring to lived experience rather than a laboratory finding. For example, a person may notice sound in unusually fine detail, need longer to shift attention, experience a delay before starting a task, become overwhelmed by a crowded environment, rely on movement to regulate, or process language more readily in writing than in real time.
These are meaningful differences in functioning. Whether they are disabling depends partly on the setting. A sensitivity to detail may be valuable in work requiring concentration, pattern recognition or careful noticing, yet exhausting in a noisy open-plan office. A need for clear instructions may create difficulty in an ambiguous workplace while being well supported by a direct, predictable manager.
This is not an argument that support needs are unreal. Some neurodivergent people have substantial and enduring disabilities, and may need accessible environments, practical support, healthcare, advocacy or personal assistance. A neurodiversity-affirming account should not minimise this. It does, however, resist treating every difference from a statistical average as evidence that the person is defective.
Why there is no diagnostic brain scan
Brain-imaging findings are usually group-level findings. The differences detected in research are generally small compared with the variation within each group. Two people with the same diagnosis may have very different cognitive profiles, sensory needs, co-occurring conditions and brain-imaging patterns. A person without a diagnosis may resemble the group average more closely than some diagnosed people on a particular measure.
This is one reason that structural MRI and machine-learning approaches have not become routine diagnostic tools for autism or ADHD. They are not accurate or robust enough for that purpose. Diagnosis, where it is wanted or useful, remains clinical and developmental: it involves patterns over time, the person’s present life, strengths and difficulties, and the contexts in which those difficulties arise.
There is another caution. Most imaging studies show association, not a simple cause. If researchers find a difference in connectivity or brain volume, they cannot automatically say that it caused a particular trait. Development is reciprocal. Experience shapes the brain, and a person’s starting neurodevelopmental profile shapes the experiences they encounter. Repeated rejection, bullying, sensory overload, chronic stress and lack of accommodation can all matter. This does not mean that trauma or parenting causes autism or ADHD; it means that people’s environments affect wellbeing and development.
Overlap is part of the picture
Large studies comparing ADHD, autism and OCD find both shared and distinct differences in brain structure. This mirrors the fact that diagnostic categories do not map neatly onto separate kinds of person. Attention, sensory processing, motor coordination, language, anxiety, compulsive experiences and emotional regulation can overlap.
Studies of both ADHD and autism have also identified different neuroanatomical subgroups within diagnostic groups and within comparison groups. That is a useful corrective to the search for a single explanation. The question is often not “What does the autistic brain look like?” but “What combination of developmental, cognitive, sensory and relational factors is shaping this person’s experience?”
What this can mean in therapy and everyday life
A thoughtful therapeutic response does not require a person to prove their neurotype through neuroscience. It begins with curiosity about their actual experience. What helps them think? What makes connection easier or harder? What happens under sensory, social or executive strain? Which adaptations have been protective, and which now carry a cost?
For some people, a history of being misunderstood can lead to masking, self-doubt, shame or exhaustion. Those experiences deserve attention without turning neurodivergence into a trauma response or suggesting that therapy should make someone neurotypical. Therapy may offer a place to understand patterns, reduce shame, negotiate needs, grieve exclusions, build self-knowledge and find relationships where difference does not have to be concealed.
The evidence is therefore both clear and limited. There is substantial evidence for differences in the development and organisation of brain systems across several neurodevelopmental profiles. There is not evidence for one uniform neurodivergent brain, for a sharp biological divide between kinds of people, or for using a brain scan to define a person. The more useful question is often how a particular person processes the world, what that costs them, what they value about it, and what would allow them to live with greater room to be themselves.
References
Boedhoe, P.S.W., van Rooij, D., Hoogman, M.
et al. (2020) ‘Subcortical brain volume, regional cortical thickness, and cortical surface area across disorders: findings from the ENIGMA ADHD, ASD, and OCD Working Groups’,
American Journal of Psychiatry, 177(9), pp. 834–843. Available at:
https://doi.org/10.1176/appi.ajp.2020.19030331.
Halliday, A.R., Vucic, S.N., Georges, B.
et al. (2024) ‘Heterogeneity and convergence across seven neuroimaging modalities: a review of the autism spectrum disorder literature’,
Frontiers in Psychiatry, 15. Available at:
https://doi.org/10.3389/fpsyt.2024.1474003.
Hoogman, M., Bralten, J., Hibar, D.P.
et al. (2017) ‘Subcortical brain volume differences in participants with attention deficit hyperactivity disorder in children and adults: a cross-sectional mega-analysis’,
The Lancet Psychiatry, 4(4), pp. 310–319. Available at:
https://doi.org/10.1016/S2215-0366(17)30049-4.
Li, T., van Rooij, D., Roth Mota, N.
et al. (2021) ‘Characterizing neuroanatomic heterogeneity in people with and without ADHD based on subcortical brain volumes’,
Journal of Child Psychology and Psychiatry, 62(9), pp. 1140–1149. Available at:
https://doi.org/10.1111/jcpp.13384.
Sha, Z., van Rooij, D., Anagnostou, E.
et al. (2022) ‘Subtly altered topological asymmetry of brain structural covariance networks in autism spectrum disorder across 43 datasets from the ENIGMA consortium’,
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https://doi.org/10.1038/s41380-022-01452-7.
