Why Does My Child Act This Way? Understanding the "Why" Behind AuDHD

In our last post, we explored exactly what AuDHD is—the co-occurrence of Autism Spectrum Disorder (ASD) and ADHD (Link to previous post).

Today, I want to dive into the question I hear most often from parents in the field: “Why on earth does my child act this way?” Let’s take a closer look at the unique patterns that emerge when these two worlds collide.

1. Is it a lack of focus, or too much of it?

This is often the most confusing part for parents.

- On some days, your child can’t sit still for even a minute.

- On other days, they are so immersed in a specific activity that they won't budge for hours.

This isn't a simple "attention problem." Rather, it’s a result of two different types of attention regulation working at the same time.

While ADHD often involves easily scattered attention, Autism involves a tendency to "hyper-focus" on specific interests.

When combined, they create what researchers call an "extreme attention profile" (Craig et al., 2015; Antshel & Russo, 2019).

In short: It is incredibly hard for them to start something they aren't interested in, and just as hard to stop something they are.

2. They love friends, but find relationships tricky

Many AuDHD children clearly want to have friends and play with others, yet they struggle with the actual mechanics of social interaction.

Research suggests a "double challenge" here: ADHD can lead to impulsive interactions that cause peer conflict, while ASD makes it harder to read subtle social cues (Joshi et al., 2013; Antshel et al., 2016). You might notice your child:

- Accidentally interrupting conversations.

- Having "off" timing during play.

- Struggling to read the other person’s reaction.

This is why parents often wonder, "They love people so much, so why is making friends so hard for them?"

3. The paradox: Loving rules but breaking them

A very common trait in AuDHD is the child who insists on rules but simultaneously breaks them.

This happens because of the tug-of-war between cognitive rigidity (from the ASD side) and impulsivity (from the ADHD side).

Studies show that while ASD makes it hard to be flexible, ADHD makes it hard to inhibit immediate behaviors (Sokolova et al., 2017; Craig et al., 2015).

Your child might deeply value the rules, but their "internal brakes" aren't strong enough to stop a sudden impulse.

It’s not intentional defiance; it’s a mismatch in their brain's behavioral control system.

4. A unique and intense sensory world

For AuDHD children, the world can feel very "loud." They may be hypersensitive to certain stimuli or, conversely, seek out intense sensory input.

Between 42% and 88% of children with ASD report sensory processing differences, and about half of children with ADHD face similar challenges (Little et al., 2018; Ben-Sasson et al., 2009). This can look like:

- Overreacting to specific sounds or lights.

- Constantly seeking certain textures or repetitive movements.

It’s helpful to view this not just as "being sensitive," but as a different way of processing the world.

5. Big, sudden emotional explosions

Emotional regulation is a common hurdle for both ASD and ADHD, and when they overlap, these "big feelings" can feel even more intense (Shaw et al., 2014; Sokolova et al., 2017).

AuDHD children tend to experience emotions with high intensity, but their "regulatory toolkit" is still under construction.

When you see a sudden meltdown or an outburst of anger, it’s often because their system has simply become overwhelmed.

6. The "Starting" Struggle (Executive Function)

Many parents tell me, "I know they can do it, but they just won't start!" This isn't a lack of motivation or a "bad attitude." It’s a challenge with Executive Function. This includes the ability to:

- Plan a task

- Initiate (start) the action

- Maintain focus

- Shift to a new task

Both ASD and ADHD involve difficulties in these areas (Willcutt et al., 2005; Craig et al., 2015).

Your child might know exactly what they need to do but feel "stuck" when it comes to actually making the first move.

Moving Forward: From "Why" to "How"

The behaviors we see in AuDHD aren't "problem behaviors"—they are the result of two different neurodevelopmental paths interacting with each other. Recent research even suggests we should view them as an overlapping spectrum rather than two separate boxes (Sokolova et al., 2017).

Instead of asking, "Why are they doing this?", we can start asking, "Which specific function is my child struggling with right now?"

In my next post, I’ll share practical ways to support AuDHD children in daily life and look at the unique strengths these children bring to the world. 

Click here to read the next post: link

 

 

Reference

Antshel, K. M., & Russo, N. (2019). Autism spectrum disorders and ADHD: Overlapping phenomenology, diagnostic issues, and treatment considerations. Current psychiatry reports, 21(5), 34.

Craig, F., Lamanna, A. L., Margari, F., Matera, E., Simone, M., & Margari, L. (2015). Overlap between autism spectrum disorders and attention deficit hyperactivity disorder: searching for distinctive/common clinical features. Autism research, 8(3), 328-337.

Joshi, G., Faraone, S. V., Wozniak, J., Tarko, L., Fried, R., Galdo, M., ... & Biederman, J. (2017). Symptom profile of ADHD in youth with high-functioning autism spectrum disorder: a comparative study in psychiatrically referred populations. Journal of Attention Disorders, 21(10), 846-855.

Leitner, Y. (2014). The co-occurrence of autism and attention deficit hyperactivity disorder in children–what do we know?. Frontiers in human neuroscience, 8, 268.

Little, L. M., Dean, E., Tomchek, S., & Dunn, W. (2018). Sensory processing patterns in autism, attention deficit hyperactivity disorder, and typical development. Physical & occupational therapy in pediatrics, 38(3), 243-254.

Shaw, P., Stringaris, A., Nigg, J., & Leibenluft, E. (2014). Emotion dysregulation in attention deficit hyperactivity disorder. American Journal of Psychiatry, 171(3), 276-293.

Sokolova, E., Oerlemans, A. M., Rommelse, N. N., Groot, P., Hartman, C. A., Glennon, J. C., ... & Buitelaar, J. K. (2017). A causal and mediation analysis of the comorbidity between attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Journal of autism and developmental disorders, 47(6), 1595-1604.

Willcutt, E. G., Doyle, A. E., Nigg, J. T., Faraone, S. V., & Pennington, B. F. (2005). Validity of the executive function theory of attention-deficit/hyperactivity disorder: a meta-analytic review. Biological psychiatry, 57(11), 1336-1346.