Down Syndrome or Autism?

If a doctor asked you to draw two columns on a piece of paper and list symptoms for DS or ASD in either, what would your list look like? Over my eight-year adventures with ER visits, hospital stays, urgent care centers, and psychology evaluations I have realized the sometimes-subtle differences between these categories.

Down Syndrome is a genetic disorder that causes developmental delays and certain physiological features. Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with both genetic and environmental influences. It is not solely a genetic disorder nor a purely psychological disorder but rather a complex condition involving brain development, genetic factors, and environmental influences.

If I were to describe the two, then I would say Down Syndrome is a way of being and Autism is a way of living or behaving within certain environments.

What’s important for families to know is that the co-occurrence of these two conditions, sometimes referred to as dual diagnosis, is more common than previously thought. According to recent studies, an estimated 16% to 18% of individuals with Down Syndrome also meet the criteria for ASD, though some research places that number closer to 20%–30%, depending on diagnostic methods and age of evaluation (Capone et al., 2020).

Why Is It So Hard to Diagnose Both?

One of the main challenges in diagnosing both conditions is that the behavioral and developmental profiles often overlap. For instance:

• Speech delay is common in both DS and ASD, but the reason behind it may differ.

• Sensory sensitivities, like avoiding textures or loud sounds, are classic ASD traits but can also be seen in some children with DS who do not have autism.

• Social behavior in DS is typically friendly and outgoing, while children with ASD may appear socially withdrawn or uninterested. However, if a child with DS shows limited eye contact, rigid routines, or intense fixations, clinicians may explore the possibility of ASD.

Yet, because many traits of ASD, like repetitive behavior or difficulty with transitions, can be misattributed to "just part of having Down Syndrome," autism can remain undiagnosed or misdiagnosed in this population for years.

When to Seek a Second Look

Parents and caregivers should trust their instincts. If a child with Down Syndrome:

• Avoids eye contact persistently

• Does not show interest in peers or caregivers

• Is extremely fixated on specific objects

• Has intense meltdowns not explained by communication challenges alone

…then it might be worth seeking a referral for an autism evaluation, even if you were initially told “it’s just the Down Syndrome.”

Most pediatricians now recommend re-evaluation between ages 4–6 as social expectations rise in preschool and kindergarten. At this stage, more nuanced behavioral differences become apparent.

What a Dual Diagnosis Means for Therapy

The good news is: early identification of both conditions can open more doors than it closes. Children with dual diagnoses often benefit from a combination of:

• Speech-language therapy that targets both expressive and pragmatic language use

• Occupational therapy focused on sensory integration and fine motor coordination

• Behavioral therapies like Applied Behavior Analysis (ABA), which can be adapted for children with intellectual disabilities

• Structured routines and visual supports to assist with transitions and expectations

Caregivers might also consider therapies like DIR/Floortime, which emphasize emotional connection and regulation, especially when ABA feels too rigid or behaviorist for their child’s learning style.

Educational Planning and IEPs

Schools often struggle to accommodate dual diagnoses due to lack of training or rigid classification systems. Be proactive with your IEP (Individualized Education Plan) team. Ensure both DS and ASD traits are addressed through accommodations and goals. This might include:

• Social skills training with neurodiverse peers

• Additional sensory breaks

• Communication systems like PECS or AAC

• Behavior intervention plans that account for sensory overload and not just defiance

Emotional Toll on Families

Dealing with a second diagnosis can feel overwhelming. Many parents describe the initial grief they felt when receiving the DS diagnosis returning in waves when ASD is added to the mix. This is normal. And valid. But just like you grew to understand and champion your child’s Down Syndrome diagnosis, you will find your footing again.

Support groups, both in-person and online, have become more open to discussing dual diagnoses. Consider searching for:

• DS-Autism Connection

• National Down Syndrome Society dual diagnosis resources

• Local parent support circles or Facebook groups specific to dual-diagnosis parenting

To those navigating this journey: you’re not alone, and your questions are valid. May your search for answers turn into a deep well of wisdom, and may your love for your child teach the world how to be kinder, more intentional, and more curious.