This article about Autism in ADHD Adults is offered by Dr Darren O’Reilly, Counselling Psychologist and Clinical Director of AuDHD Psychiatry.
The Overlap You Might Be Missing: Autism in ADHD Adults
If you have an ADHD diagnosis, you already know something about how your brain works differently. But for a significant number of adults with ADHD, that diagnosis only tells part of the story. Research consistently shows that between 20% and 50% of adults with ADHD also show clinically s
ignificant autism spectrum disorder (ASD) traits (Hours et al., 2022). This is commonly called AuDHD, a co-occurrence that clinicians increasingly recognise as an overlapping and interacting profile. Yet autism in adults with ADHD is frequently missed, sometimes for decades, because the diagnostic picture is genuinely complex and because each condition can conceal features of the other.
For adults who suspect this might apply to them, seeking a specialist autism assessment for adults is often the point at which years of unexplained difficulties, such as patterns that persisted even after ADHD was identified and supported, finally come into focus.
Autism in ADHD: Why ADHD and Autism Are So Often Found Together
Though the term is not a clinical name, AuDHD is not coincidental. Genetic research has found that the two conditions share substantial genetic risk: nearly half the genetic variance in autism overlaps with ADHD (Hours et al., 2022). Twin and family studies consistently support a strong shared genetic signal.
The figures are striking. A 2021 meta-analysis of 63 studies found that the lifetime prevalence of ADHD in autistic individuals is approximately 40.2% (Rong et al., 2021). From the other direction, as we’ve previously mentioned, studies estimate that between 20% and 50% of those diagnosed with ADHD also display clinically significant autistic traits (Hours et al., 2022). These are not marginal overlaps; they describe a population of considerable size that routinely navigates life with an incomplete neurological picture.
Autism in ADHD: How Each Condition Hides the Other
One of the central reasons autism goes undetected in adults with ADHD is that the two conditions actively obscure each other. Research has documented this bidirectional masking: ADHD traits such as impulsivity, talkativeness, and social approach behaviour can superficially resemble neurotypical social engagement, making autistic social communication differences harder to detect. Conversely, the intense focus and routine-seeking of autism can dampen the hyperactivity and distractibility associated with ADHD, making ADHD appear less severe (or presenting differently than expected) (Cortese et al., 2025).
A prior ADHD diagnosis has been specifically identified as a factor associated with significantly later autism diagnosis because existing diagnoses bias clinical attribution of new symptoms toward what is already known (Visser et al., 2019). Adults in this situation often describe a long history of ADHD support that helped with some things, but never quite accounted for everything.
What Autism Looks Like When ADHD Is Already in the Picture
In adults who have grown up with unidentified autism alongside their ADHD, the autistic profile tends to present in ways that can be easy to attribute to other causes. Research comparing self-reported symptoms across adults with ADHD only, autism only, and both conditions found distinct patterns: those with co-occurring ASD and ADHD showed significantly greater affective lability and more pronounced social communication differences than those with ADHD alone, alongside greater sensory sensitivity and a stronger need for routine and predictability (Pehlivanidis et al., 2025).
In practice, this can show up as:
• Social exhaustion: Social interactions feel genuinely effortful in a way that rest alone does not resolve; social rules feel opaque rather than simply tiring.
• Sensory sensitivities that feel physical: Specific sounds, textures, lighting, or crowded environments cause disproportionate distress that is not explained by distractibility alone.
• An unusually strong pull toward routine: not simply a preference for structure, but a sense of genuine disorientation or distress when sequences are disrupted
• Deep, consuming interests: intense and sustained focus on specific areas that provides meaning and comfort, distinct from ADHD hyperfocus in its consistency and depth
• Persistent difficulties that ADHD support does not fully address: treatments and strategies targeted at ADHD help, but leave significant areas of daily life unexplained or unsupported
The Cost of a Missing Diagnosis
Going without an autism diagnosis when one is warranted carries real consequences. Three major domains of impact are: mental health, daily functioning, and social connection. Undiagnosed adults showed elevated rates of depression, anxiety, and in some cases substance use, alongside greater difficulties in relationships and employment. Critically, many had received years of treatment for these secondary presentations without the underlying neurodevelopmental profile being identified (French et al., 2023).
Camouflaging or masking, the sustained effort to mask autistic traits in social contexts, is a key mechanism here. A study comparing masking across adults with autism, ADHD, and co-occurring presentations found that camouflaging was significantly more pronounced in autism and in the combined AuDHD group, and that it was strongly associated with poorer mental health outcomes (van der Putten et al., 2024). Adults who have been masking for decades without knowing they were doing so often carry the effects in ways they have never been able to fully explain.
What Changes With an Accurate Diagnosis
Understanding the possibility of co-occurring autism can change how a person makes sense of their own experience. Clinical guidance emphasises that when autism is considered alongside ADHD, assessment needs to account for masking, differences in presentation across gender, and the way an existing diagnosis can shape how difficulties are interpreted (Carlisle et al., 2024). More broadly, it highlights the importance of looking at the full neurological profile rather than viewing each difficulty in isolation.
For many adults, recognising this overlap shifts how long-standing patterns are understood. This can involve:
• Moving from seeing certain difficulties as personal shortcomings to recognising them as consistent neurological patterns.
• Understanding why some challenges persisted even when ADHD was being actively supported.
• Reinterpreting past experiences (particularly around social interaction and overwhelm) in a way that feels more coherent.
• Recognising that seemingly conflicting traits can exist together within the same profile.
These shifts do not change the underlying experience, but they can change how that experience is organised and understood.
Conclusion
ADHD and autism overlap far more than has historically been recognised, and that overlap has meaningful implications for how people understand their own experiences. When only one part of that picture is identified, the rest can remain difficult to name, even when it is consistently present.
For adults with ADHD who have found that certain patterns have never been fully explained, this may reflect a broader neurological profile rather than a series of unrelated difficulties. Recognising that possibility does not require immediate conclusions. But for many people, it provides a more coherent way of understanding experiences that have long felt fragmented or incomplete.
References
Carlisle, A., Phillips, B., & Wan, M. (2024). Diagnosing autism in adults: Clinically focused recommendations. Journal of Health Service Psychology, 50(2), 103–111. https://doi.org/10.1007/s42843-024-00108-0
Cortese, S., et al. (2025). An update on the comorbidity of attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) and its clinical management. Expert Review of Neurotherapeutics. https://doi.org/10.1080/14737175.2025.2599856
French, B., Daley, D., Groom, M., & Cassidy, S. (2023). Risks associated with undiagnosed ADHD and/or autism: A mixed-method systematic review. Journal of Attention Disorders, 27(12), 1393–1410. https://doi.org/10.1177/10870547231176862
Hours, C., Recasens, C., & Baleyte, J.-M. (2022). ASD and ADHD comorbidity: What are we talking about? Frontiers in Psychiatry, 13, 837424. https://doi.org/10.3389/fpsyt.2022.837424
Pehlivanidis, A., Kouklari, E.-C., Kalantzi, E., et al. (2025). Self-reported symptoms of attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and affective lability in discriminating adult ADHD, ASD and their co-occurrence. BMC Psychiatry, 25, 391. https://doi.org/10.1186/s12888-025-06841-0
Rong, Y., Yang, C. J., Jin, Y., & Wang, Y. (2021). Prevalence of attention-deficit/hyperactivity disorder in individuals with autism spectrum disorder: A meta-analysis. Research in Autism Spectrum Disorders, 83, 101759. https://doi.org/10.1016/j.rasd.2021.101759
van der Putten, W. J., Mol, A. J. J., Groenman, A. P., Radhoe, T. A., Torenvliet, C., Agelink van Rentergem, J. A., & Geurts, H. M. (2024). Is camouflaging unique for autism? A comparison of camouflaging between adults with autism and ADHD. Autism Research, 17(4), 812–823. https://doi.org/10.1002/aur.3099
Visser, J. C., Rommelse, N. N. J., Greven, C. U., & Buitelaar, J. K. (2019). Delayed autism spectrum disorder recognition in children and adolescents previously diagnosed with attention-deficit/hyperactivity disorder. Frontiers in Psychiatry, 10, 260. https://doi.org/10.3389/fpsyt.2019.00260
About the Author
Dr. Darren O’Reilly is the neurodivergent founder and CEO of AuDHD Psychiatry – a UK clinic dedicated to evidence-based neurodivergent care. The clinic provides private online ADHD, Autism, and combined (AuDHD) assessments for adults and children across the UK. Its multidisciplinary team of psychologists, consultant psychiatrists, prescribers, and ADHD coaches offers compassionate, evidence-based diagnosis, medication, and ongoing support, helping clients gain clarity, confidence, and faster access to care.
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Please note the Living Autism services are now being delivered at MM Consultancy for Neurodiversity.
