AuDHD Blog
Why Autism and ADHD Were Historically Missed Together
The history of diagnostic separation helps explain why many people were assessed through only one lens, even when both autism and ADHD were part of the picture.
Diagnosis · · 9 min read
Many late-recognized AuDHD adults were not missed because their experiences were imaginary. They were often assessed inside systems that had been trained to separate autism and ADHD, even when the real person in front of them showed both sets of needs (Leitner, 2014; Young et al., 2020).
The old diagnostic map
Earlier diagnostic systems discouraged or excluded dual diagnosis. Leitner (2014) describes how DSM-IV treated autism spectrum disorder as an exclusion criterion for ADHD, and Young et al. (2020) note that DSM-5 was important because it formally allowed ADHD and autism to be recognized together.
That change did not make co-occurrence suddenly appear. It made an already visible clinical reality easier to name.
Why overlap was still visible
Rommelse et al. (2010) summarized evidence that approximately 20%-50% of children with ADHD met autism spectrum disorder criteria and approximately 30%-80% of autistic children met ADHD criteria. Those are broad, older child-focused estimates, but they show why the old either-or framing was scientifically fragile.
Hours et al. (2022) add the important caution: high overlap can reflect true co-occurrence, shared mechanisms, measurement overlap, developmental change, or symptom misinterpretation. That is why careful assessment matters more than headline numbers.
The adult cost
For adults, especially people whose presentation was shaped by gendered expectations, masking, or high performance in some areas, diagnostic separation could mean years of partial explanations. Craddock (2024a) describes how adulthood combined diagnosis helped AuDHD women reinterpret histories that had been filtered through gendered expectations and misrecognition.
A missed pathway is not always one missed appointment. Sometimes it is years of being understood through only half the map.
The better question now
The current question is not whether autism and ADHD are allowed to co-exist. They are. The better question is whether assessment and support are actually checking both, considering development and context, and avoiding the assumption that one diagnosis explains every difficulty (Young et al., 2020).
If you were missed
Late recognition can bring relief, grief, anger, and confusion at the same time. A missed diagnosis does not mean you failed to explain yourself correctly. Diagnostic history, conceptual confusion, masking, stereotypes, and uneven access can all contribute to people being understood through only one lens (Craddock, 2024a; Hours et al., 2022; Young et al., 2020).
- Let the history be complex. Do not force one explanation for every missed sign.
- Revisit old labels carefully: anxiety, laziness, giftedness, oppositionality, sensitivity, depression, or "not trying" may have hidden support needs.
- Look for patterns across settings rather than isolated memories.
- Use new language to build support, not to punish your past self for not knowing sooner.
What to gather before assessment
If you are seeking assessment, preparation can help because short appointments may miss context. Young et al. (2020) recommend structured identification and supporting information across settings, which means your examples should show both history and current daily impact.
- Childhood examples: school reports, family observations, sensory patterns, friendships, routines, activity level, attention, and emotional regulation.
- Current examples: work, study, home care, relationships, money, health admin, sleep, eating, sensory load, and transition difficulty.
- Masking examples: what you hide, script, suppress, compensate for, or recover from afterward.
- Previous supports: what helped, what failed, and what became another demand.
Why late recognition feels disorienting
Late recognition can reorder a life story. The point is not only "now I have the right labels." It is also realizing how many old explanations may have been incomplete: lazy, intense, sensitive, gifted, dramatic, anxious, underachieving, too much, not enough. Adult AuDHD research shows how combined diagnosis can help people reinterpret gendered expectations, masking, and years of misrecognition (Craddock, 2024a).
- Expect mixed feelings. Relief and grief can arrive together.
- Use the new frame to identify support, not to relitigate every past moment at once.
- Look for repeated patterns across school, work, relationships, sensory environments, and home life.
- Let uncertainty remain where the evidence is incomplete. A careful map is still useful before every detail is settled (Hours et al., 2022).
Why the old rule still echoes
Even after diagnostic rules changed, services and public expectations do not update overnight. Some adults still meet clinicians, teachers, managers, or relatives whose mental model was built when autism and ADHD were treated as separate explanations. That history matters because it can shape which questions get asked, which records are interpreted, and which supports are offered (Hours et al., 2022; Young et al., 2020).
- If one diagnosis is already known, ask directly whether the other has been considered rather than assuming it was ruled out.
- If old reports mention attention, social, sensory, or behavior concerns separately, bring them together as context.
- If a professional says one label explains everything, ask what evidence supports that and what evidence would change the picture.
- If you were missed, treat the old pathway as incomplete information, not proof that your current understanding is invalid.
References
- Craddock, E. (2024a). Being a woman is 100% significant to my experiences of attention deficit hyperactivity disorder and autism: Exploring the gendered implications of an adulthood combined autism and attention deficit hyperactivity disorder diagnosis. *Qualitative Health Research, 34*(14), 1442-1455. https://doi.org/10.1177/10497323241253412
- Hours, C., Recasens, C., & Baleyte, J. M. (2022). ASD and ADHD comorbidity: What are we talking about? *Frontiers in Psychiatry, 13*. https://doi.org/10.3389/fpsyt.2022.837424
- Leitner, Y. (2014). The co-occurrence of autism and attention deficit hyperactivity disorder in children: What do we know? *Frontiers in Human Neuroscience, 8*. https://doi.org/10.3389/fnhum.2014.00268
- Rommelse, N. N. J., Franke, B., Geurts, H. M., Hartman, C. A., & Buitelaar, J. K. (2010). Shared heritability of attention-deficit/hyperactivity disorder and autism spectrum disorder. *European Child & Adolescent Psychiatry, 19*(3), 281-295. https://doi.org/10.1007/s00787-010-0092-x
- Young, S., Hollingdale, J., Absoud, M., Bolton, P., Branney, P., Colley, W., Craze, E., Dave, M., Deeley, Q., Farrag, E., Gudjonsson, G., Hill, P., Liang, H. L., Murphy, C., Mackintosh, P., Murin, M., O'Regan, F., Ougrin, D., Rios, P., ... Woodhouse, E. (2020). Guidance for identification and treatment of individuals with attention deficit/hyperactivity disorder and autism spectrum disorder based upon expert consensus. *BMC Medicine, 18*(1). https://doi.org/10.1186/s12916-020-01585-y