A Diagnostic Separation That Shaped a Generation
For most of the modern history of psychiatry, autism and ADHD were treated as mutually exclusive conditions. Clinicians were trained to look for one or the other. Until the publication of DSM-5 in 2013, a dual diagnosis was formally discouraged within diagnostic criteria.
That structural separation influenced research design, clinical training and public understanding. It also meant that individuals whose neurodevelopmental profile spanned both spectrums were frequently described in partial terms. One half of the picture was acknowledged. The other was often overlooked.
In the decade since diagnostic rules changed, evidence has steadily accumulated that co-occurrence is common rather than exceptional. A 2014 review published in Frontiers in Human Neuroscience by Y. Leitner reported that between 30 and 50 percent of autistic individuals meet criteria for ADHD, though estimates vary widely across studies depending on sampling and methodology, with some reporting rates as high as 70 percent. Subsequent reviews, including work by Antshel and Russo in Current Psychiatry Reports in 2019, have explored the shared genetic and neurocognitive features underlying both conditions.
Yet public discussion continues to frame autism and ADHD as separate lanes rather than intersecting systems.
Shared Pathways, Distinct Expressions
Autism and ADHD are both neurodevelopmental conditions involving differences in executive functioning, attention regulation and sensory processing. Neuroimaging research has identified overlapping patterns in frontostriatal circuitry and dopamine regulation, systems associated with reward processing and behavioural control.
Genetic studies have also demonstrated partial heritability overlap. Large-scale analyses, including work emerging from the Psychiatric Genomics Consortium, suggest that common genetic variants contribute risk to both conditions.
Despite these shared foundations, behavioural expression can appear divergent. Autism is typically associated with differences in social communication and a preference for predictability. ADHD is linked to attentional variability, impulsivity and novelty seeking.
When these profiles co-occur, the internal experience may feel contradictory. A person may rely on structure to remain regulated while simultaneously struggling to sustain that structure. Sensory sensitivities may coexist with a drive for stimulation. Hyperfocus may sit alongside task initiation paralysis.
These are not inconsistencies in character. They reflect the interaction of multiple regulatory systems operating at once.
Why Co-Occurrence Complicates Recognition
Clinical assessment frameworks were built on separation. As a result, traits that belong to one condition may obscure or reinterpret traits belonging to the other.
In children, hyperactivity may draw attention first, delaying recognition of social processing differences. In adults, especially those who have adapted their behaviour over many years, one set of traits can mask the presence of another.
Research into diagnostic patterns has highlighted this complexity. Studies have shown that adults receiving stimulant medication for ADHD sometimes report that reduced hyperactivity makes previously manageable sensory or social differences more noticeable. Conversely, autistic traits may be misattributed to anxiety or inattention.
The result is often a fragmented narrative. Individuals are told they are anxious, inconsistent or over-sensitive long before anyone considers an integrated neurodevelopmental explanation.
The Emergence of AuDHD as a Descriptive Term
The term AuDHD has emerged organically within neurodivergent communities to describe this dual presentation. It is not a formal diagnostic category, and it does not replace established clinical criteria. Rather, it reflects the recognition that co-occurrence can create a composite neurotype with its own regulatory patterns.
In my own work with late-diagnosed adults, many describe a persistent internal tension between competing drives. In writing Autism, ADHD and Me: Your No Bullshit Guide to Life After Diagnosis, I encountered repeated accounts of individuals who felt they were “too much and not enough at the same time,” a phrase that echoes the layered nature of this profile.
While anecdotal accounts do not constitute empirical evidence, they often illuminate areas where formal research is still evolving.
Increasingly, academic literature is moving toward dimensional models of neurodevelopment rather than rigid categorical boundaries. The National Institute of Mental Health’s Research Domain Criteria initiative, for example, has encouraged examination of shared cognitive and biological systems across diagnostic labels.
Within that framework, co-occurring autism and ADHD cease to look anomalous. They appear instead as overlapping expressions within broader regulatory networks.
Toward a More Integrated Understanding
Recognition of dual presentation has implications beyond terminology. It affects clinical assessment, pharmacological decisions and workplace or educational support strategies. It shapes how individuals understand their own cognitive patterns.
When autism and ADHD are considered in isolation, nuance is lost. When they are examined together, a more coherent explanation often emerges.
The science is still developing. Longitudinal studies that specifically examine co-occurring presentations remain limited, and much of the current evidence relies on cross-sectional data. Yet the direction of research is clear: separation does not reflect lived complexity.
As diagnostic frameworks evolve, the question is no longer whether autism and ADHD can co-occur. It is how best to understand the interaction between them.
For many adults who have spent years trying to reconcile seemingly opposing traits, that shift represents not a new label, but a clearer map.
Author Bio
Jenny Lucas is a UK-based author of Autism, ADHD and Me: Your No Bullshit Guide to Life After Diagnosis and a former secondary school teacher. She writes and speaks on late diagnosis, neurodiversity and the intersection of health, identity and workplace systems.
