Attention Deficit/Hyperactive Disorder (ADHD) and autism, as well as a variety of developmental delays and disorders, can have many symptoms in common.

So, when we see our children exhibiting behaviors or signs associated with one when they’ve already been diagnosed with the other, should we look for a second diagnosis? How common is it for the two to be diagnosed in the same child?

A new study found high comorbidity, suggesting that an evaluation could be a good idea, even if your child is already diagnosed.

New Study Examines Comorbidity Of ADHD & Autism

The new study conducted in Spain finds that as many as a third of kids who meet the diagnostic criteria for autism also meet the diagnostic criteria for ADHD. The total percentage of kids who could be diagnosed with both was around 3.2% (to be exact, 3.19% based on parent reporting of symptoms and 3.17% based on teacher reporting of symptoms).

Of students with sufficient symptoms to qualify for a diagnosis of Autism Spectrum Disorder (ASD), 32.8% also presented with ADHD symptoms. The study also examined students who had reported ASD symptoms but below the threshold for diagnosis and found that among these, 31.4% met the criteria for an ADHD diagnosis as well, according to a PsyPost analysis.

What Do These Numbers Mean For Parents, Teachers, & Kids?

Notably, both the students who meet the criteria for an autism diagnosis and those who show some signs of ASD but do not meet the requirements for a diagnosis have similar rates of ADHD. Further investigation of this could potentially change outlooks on the threshold for diagnosis.

More directly, it suggests that even if we as parents or teachers don’t see all the struggles, we should be aware that kids who demonstrate a need for support in some areas may have additional support needs that aren’t as obvious. It means that if we see a child show signs of ADHD or autism, and they already have a diagnosis of one of the two, we shouldn’t immediately write off those signs as being connected to the current diagnosis but should instead consider whether further evaluation may be in order.

Why Are Diagnoses Of ADHD & Autism Rising?

Diagnostic criteria have already changed.

In 2013 (over a decade ago!), the diagnosis of “Asperger’s syndrome” was removed from the DSM. It was a term for people who had some of the same neurological differences that were already classified as autism but were deemed to have a “milder” or “lesser” form of it.

Now that term has been removed, “functioning” labels (such as “high-functioning autism”) are falling out of use, and instead, the focus is on the level of support needs an individual has. Those with higher support needs and those with lower support needs all fall on the spectrum — Autism Spectrum Disorder.

While autism and ADHD themselves are not gendered, the ways they present in students can differ by gender, in large part due to social norms. For decades, diagnosis has centered around the ways ADHD and autism are most likely to present in boys, leaving girls overlooked.

Why Does Diagnosis Matter?

Children and Adults with Attention-Deficit/Hyperactivity Disorder (CHADD) is an organization that works to promote evidence-based information about ADHD and bring more support for those who need it. They shared information from Arthur Robin, PhD, a professor of psychiatry and behavioral neurosciences and pediatrics:

“The adult women with ADHD I encounter in my practice feel like something is wrong with them,” says Dr. Robin. “They feel like second-class citizens with poor self-esteem, and they often try to hide their difficulties and true natures from others.”

There has been an increase of over 300% of prescriptions for ADHD meds filled for women and teen girls between the ages of 15 and 44, demonstrating that these women who went undiagnosed in early childhood are finally getting diagnoses and treatments.

Those who have symptoms of ADHD or ASD but do not get evaluated can feel like they spend their whole lives struggling to fit in or to do tasks that are easier for their neurotypical peers, but without understanding why.