Dual Diagnosis of Down Syndrome and Autism Spectrum Disorder

In the recent past, there was a misconception that individuals with Down Syndrome (DS) can not have Autism Spectrum Disorder (ASD) because they tend to be social. However, leading research suggests that about 20% of individuals with DS meet diagnostic criteria for ASD (Versaci et al., 2021). This blog post will provide information about DS, ASD, and the dual diagnosis of Down Syndrome and ASD (DS-ASD), as well as considerations of Intellectual Disability (ID). 

Down Syndrome (DS) Overview

According to the Centers for Disease Control and Prevention, “Down Syndrome is a condition in which an individual has an extra chromosome” and occurs in about 1 in 700 babies (CDC, 2023). Due to the physical characteristics of the condition, as well as screening and diagnostic testing that can be administered as early as 10 to 15 weeks of pregnancy (Penn Medicine, 2021; Mayo Clinic, 2018), individuals with DS are typically diagnosed in pregnancy and at birth or shortly thereafter (NADS, n.d.). 

Per a webpage on Down Syndrome, written by Boston Children’s Hospital, individuals with DS “often have mild to moderate intellectual disability and may have specific challenges with attention span, verbal memory, and expressive communication” (BCH, n.d.). Despite challenges in expressive communication, individuals with DS typically have strong social skills and use nonverbal communication to socially interact with others (BCH, n.d.).

Autism Spectrum Disorder (ASD) Overview

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by difficulties in social communication and interaction as well as restricted or repetitive behaviors or interests. About 1 in 36 children have been identified with ASD, and the average age of diagnosis is 4 years and 4 months old (CDC, 2023). Some behavioral characteristics include:

Social Communication and Interaction Characteristics:

• Little to no eye contact
• Limited facial expressions
• Difficulties recognizing and expressing individual emotions and recognizing emotions in others
• If there is spoken language, unusual intonation 

Restricted or Repetitive Behaviors or Interests

• Lining up of toys
• Repeats words or phrases (may include same intonation patterns)
• Repetitive use of objects and repetitive body movements
• Need for routine; resistance to change
• Narrow or all encompassing interests

Dual-diagnosis of Down Syndrome and ASD (DS-ASD)

There is a growing body of research pertaining to the dual diagnosis of DS-ASD. In a research article by Versaci, Mattie, and Imming (2021), researchers compiled and analyzed the current evidence base of ASD in DS. They outlined the following behavioral profile for individuals with DS-ASD:

• In early development, there are difficulties in social-emotional reciprocity (engaging in back-and-forth social interaction) similar to individuals with DS and severe cognitive impairment 
• Poorer communication skills than individuals with DS alone
• Increased difficulties with: 
  • anxiety
  • irritability
  • difficulty with transitions
  • hyperactivity, withdrawal
  • attention problems
  • sleep disturbances 
• Higher rates of stereotyped behaviors (repeated movements/actions) than those with DS alone, including:
  • vocalizations such as howling or growling
  • repetitive motor behaviors such as teeth grinding or hand flapping
  • feeding problems such as food refusal or unusually strong preferences
  • self-injurious behaviors such as biting or hitting
  • response to sensory input such as attraction to lights and spinning objects

Intellectual Disability (ID) Considerations

Assessing for ASD in DS when ID is present has proven difficult for mental health practitioners as it is challenging to differentiate what symptoms are derived from ID versus from potential ASD. In a study conducted by Wester Oxelgren et al. in 2019, researchers looked at the differences between DS-ASD with severe ID versus DS alone with severe ID. They found that “children with DS, ASD and severe ID had more autism symptoms compared to those with DS and severe ID but without ASD” (Oxelgren et al., 2019). Autism symptoms were measured by scoring the Autism Diagnostic Observation Schedule – Second Edition (ADOS-2), an assessment tool that mental health clinicians use to diagnose ASD. The ADOS-2 is comprised of three categories that assess for symptoms of ASD which include verbal and non-verbal communication, reciprocal social interaction, and stereotyped behaviors and restricted interests. Additionally, researchers found that children with DS-ASD and severe ID had higher scores (or more severe symptoms) in the ADOS-2 items ‘frequency of vocalization directed to others’ ‘Unusual repetitive behaviors or stereotyped behaviors,’ ‘Quality of social overtures,’ and ‘unusual eye contact’ than children with DS alone and severe ID. 

If you suspect your child with DS may also have ASD, reach out to a specialized provider in cognitive impairments, such as a developmental behavioral pediatrician or a psychologist who specializes in ASD.

References:

Boston Children’s Hospital. (n.d.). Down syndrome. Boston Children’s Hospital. https://www.childrenshospital.org/conditions/down-syndrome#:~:text=Behavioral%20problems%20such%20as%20stubbornness,syndrome%20have%20strong%20social%20skills.

Centers for Disease Control and Prevention. (2023, April 4). Data & statistics on autism spectrum disorder. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/autism/data.html 

Centers for Disease Control and Prevention. (2023, June 28). Facts about down syndrome. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/birthdefects/downsyndrome.html#:~:text=How%20Many%20Babies%20are%20Born,1%20i%20every%20700%20babies.

Centers for Disease Control and Prevention. (2022, March 28). Signs and symptoms of autism spectrum disorders. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/autism/signs.html 

Mayo Foundation for Medical Education and Research. (2018, March 8). Down syndrome. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/down-syndrome/diagnosis-treatment/drc-20355983#:~:text=Diagnostic%20tests%20that%20can%20identify,and%2013%20weeks%20of%20pregnancy. 

National Association for Down Syndrome. (n.d.). Facts about down syndrome. National Association for Down Syndrome. https://www.nads.org/resources/facts-about-down-syndrome/#:~:text=Diagnosis,in%20babies%20with%20Down%20syndrome. 

Penn Medicine. (2021, December 30). Screening for Down Syndrome. Penn Medicine. https://www.pennmedicine.org/updates/blogs/womens-health/2012/august/screening-for-down-syndrome#:~:text=Screening%20for%20Down%20syndrome%20can,multiple%20marker%20serum%20screening%20test. 

Versaci, T. M., Mattie, L. J., & Imming, L. J. (2021). Down syndrome and autism spectrum disorder dual diagnosis: Important considerations for speech-language pathologists. American Journal of Speech-Language Pathology, 30(1), 34–46. https://doi.org/10.1044/2020_ajslp-20-00050 

Wester Oxelgren, U., Åberg, M., Myrelid, Å., Annerén, G., Westerlund, J., Gustafsson, J., & Fernell, E. (2019). Autism needs to be considered in children with down syndrome. Acta Paediatrica, 108(11), 2019–2026. https://doi.org/10.1111/apa.14850