Part 2: Autism & ADHD – Overlap, Co-occurrence, and Why It Matters

Intro / Recap

In Part 1, we explored the key traits and differences of Autism and ADHD. Now, let’s look at how these neurotypes overlap, co-occur, and shape lived experience.

Understanding the Autism and ADHD Overlap

When autism and ADHD occur together—a combination often called AuDHD—the overlap can make it tricky to recognize where one neurotype ends and the other begins.

Though distinct, Autism and ADHD share many traits:

• Differences in sensory processing

• Stimming or fidgeting

• Challenges managing impulses

• Social behaviors that differ from neurotypical expectations

• Distinct communication patterns, such as info-dumping, or sharing about a personal experience after someone else shares, to relate.

• Differences in executive functioning, including emotion regulation

• Difficulty switching between tasks

• Passionate interests and hyperfocus

For a deeper dive on the similarities and differences, check out this image below.

Co-Occurrence and Research Insights

Historically, Autism and ADHD couldn’t be diagnosed together until the DSM-V. Today, research shows:

• Autism and ADHD share genetic heritability, often running together in families (Antshel & Russo, 2019; Sokolova et al., 2017)

• 20–83% of Autistic children may also meet criteria for ADHD

• 30–65% of ADHD children display Autistic traits

Brain studies show so much neurobiological overlap between Autism, ADHD, and even OCD that some researchers propose thinking of them along a continuum rather than separate categories (Deserno et al., 2023).

When someone is both Autistic and an ADHDer, they often refer to themsleves as AuDHD (an Autistic ADHDer).

ADHD Masking Autism: How One Can Hide the Other

ADHD can mask Autism, Autism can mask ADHD, which can make receiving an Autism diagnosis or an ADHD diagnosis more challenging. For example:

• Impulsivity may mask a need for predictability

• Social differences may be misattributed to attention issues

This can lead to misdiagnosis, or late-diagnosed Autism or late-diagnosed ADHD, especially for those who have non-stereotypical presentations, or who have learned to mask their traits / engage in compensatory strategies.

Next, we'll discuss Autism and ADHD co-occurring, which means when they occur together at the same time.

Key Findings About Co-Occurrence

• Autism diagnoses can be delayed up to five years when ADHD is present (Miodovnik et al., 2015)

• 40–70% of Autistic people show clinically significant ADHD traits

• 20–60% of ADHDers show social and communication differences often seen in Autism (Antshel & Russo, 2019)

• 15–64% of ADHDers display higher levels of Autistic traits compared to non-ADHDers

• When Autism is diagnosed first, ADHD is usually identified earlier; when ADHD comes first, Autism tends to be diagnosed later

Why This Matters

Recognizing the full picture of Autism and ADHD together—or AuDHD—can help neurodivergent adults find self-understanding and support that honors all parts of their experience.

Understanding both sides of your neurotype can bring clarity, self-compassion, and better support.

If “just ADHD” or “just Autistic” has never captured your full experience, you’re not alone. Both identities can coexist, interact, and shape how you move through the world.

Finding a provider or assessor who understands both Autism and ADHD, especially non-stereotypical presentations and masking, can make a huge difference in validation and care.

Many adults reach out after realizing that their experiences may reflect both Autism and ADHD.

At The Divergent Grove Therapy, I specialize in affirming assessments and therapy for Autistic, ADHD, and AuDHD adults.

Schedule your consult or learn more about services here ⬇️.

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Want more?

Dr. Megan Anna Neff, of Neurodivergent Insights provides a deeper dive into the overlaps and differences, and a lot of the information from this series comes from their blog post, and their research. Head here full their full blog post. They're also my #1 recommended resource.

FYI - If you are a past or current therapy or assessment participant - I have a license to share all their digital downloads.

Resources

Antshel, K. M., & Russo, N. (2019). Autism spectrum disorders and ADHD: Overlapping phenomenology, diagnostic issues, and treatment considerations. Current Psychiatry Reports, 21(5), 34. https://doi.org/10.1007/s11920-019-1020-5

Deserno, M. K., et al. (2023). The ADHD–Autism spectrum disorder spectrum: Distinct disorders or continuum? Neuroscience & Biobehavioral Reviews, 149, 105157. https://doi.org/10.1016/j.neubiorev.2023.105157

Krakowski, A. D., et al. (2020). Unraveling the overlap: Autism spectrum disorder and attention-deficit/hyperactivity disorder in children. Frontiers in Psychiatry, 11, 761. https://doi.org/10.3389/fpsyt.2020.00761

Miodovnik, A., Harstad, E., Sideridis, G., & Huntington, N. (2015). Timing of the diagnosis of attention-deficit/hyperactivity disorder and autism spectrum disorder. Pediatrics, 136(4), e830–e837. https://doi.org/10.1542/peds.2015-1502

Waldren, R., et al. (2024). Attentional control as a shared mechanism in ADHD and autism spectrum disorder: A meta-analytic review. Journal of Neurodevelopmental Disorders, 16(1), 22. https://doi.org/10.1186/s11689-024-0956-1

Zhong, Y., & Porter, M. A. (2024). Autism and ADHD traits in adults: A meta-analysis of prevalence and overlap. Autism Research, 17(2), 215–230. https://doi.org/10.1002/aur.3142

Neff, M, A. (2022). ADHD vs. Autism: Key differences, overlaps, and shared traits. Neurodivergent Insights. Retrieved October 24, 2025, from https://neurodivergentinsights.com/adhd-vs-autism/#genetics