Putting the Pieces Together

The Down Syndrome-Autism Intersection

By Susan Fawcett, M.Sc., RSLP, PhD Candidate and Glen Hoos

Susan Fawcett is Director of Therapy, Behaviour and Family Support at the Down Syndrome Resource Foundation. Glen Hoos is Director of Communications at the Down Syndrome Resource Foundation, and the father of Becca.

When Becca was born, we had a whole lot to learn about Down syndrome. Like most parents of a new baby, we never imagined our child would be anything other than typical and healthy. And so, we embarked upon a journey of discovery, guided by a team of doctors, specialists, and support workers.

The system just loves to categorize kids – even those who defy the usual categories. As the experts set aside the growth and development charts they use for typical children, they introduced us to the norms and expectations for children with Down syndrome. She should be this size by this age (Becca is off the bottom of the growth charts). She should be crawling by one and walking by two (Becca never crawled, and walked at four-and-a-half). She should be potty trained by the age of seven (at 15, it’s still a major work in progress).

It’s all been incredibly discouraging. Every step of the way, Becca has seemed to be behind her peers – not just typical children her age, but also many other children with Down syndrome.

It’s not just her physical development, either. We started noticing some odd patterns of behaviour that didn’t seem to fit with the Down syndrome profile. As a young child, Becca’s favourite playtime activities were tiling her entire bedroom floor and bed with board books, and taking all her Little People figures and lining them up in one long, straight line.

She was also a major stasher. She would remove the grates from floor vents and stuff the vents with toys and food. She would hide everything, including the shoes of visitors we invited over. Often, she would even hide her own favourite toys and then forget where she put them, causing great upset when she then had to make do without them for weeks or even months at a time.

Even today in her mid-teen years, she hides food all over the house. We find dried out tortillas in between the LP’s in our record collection, wieners between the couch cushions, and boxes of long-thawed frozen food in all sorts of creative places.

The stereotype of people with Down syndrome being easy-going and happy-go-lucky is questionable to begin with, but Becca is on the extreme opposite end. Her need to be in control is so strong that she often gets stuck, refusing to move and therefore missing out on things that she herself desires to do because an unspoken precondition has not been met in just the right way.

The professionals on her team noticed the differences as well. She was diagnosed first with anxiety, and later with OCD. However, it wasn’t until her early teens that it became clear something more was at play. Finally, at the age of 14, Becca received a dual diagnosis of autism. It was “a slam dunk” case, said the developmental psychologist who made the final call.

Why then did it take so long to diagnose?

Prevalence of Autism in Down Syndrome

Traditional thinking held that autism was rare in people with Down syndrome, but that is far from the case. In fact, it is estimated that autism in individuals with Down syndrome is 10-25 times more common than in the typical population.[i] At the Down Syndrome Resource Foundation, our prevalence rate is in line with these studies, with approximately 12% of our students having a dual diagnosis. However, this diagnosis often comes much later than it would for an otherwise typical child.

In fact, Becca’s case is quite common. In one study of subjects with a dual diagnosis, the mean age of autism diagnosis was 14.4 years[ii] – this despite the fact that, as with other children, autistic symptoms are present much earlier in life (rarely do they emerge in kids after the age of three, whether or not they have Down syndrome).

This delayed diagnosis creates many problems. Clearly, children with a dual diagnosis are at a real disadvantage in their development and education, even relative to children with only one of the disabilities. Even more problematic are the faulty expectations that may be placed on the child where the autism has gone undetected. As one study concluded, “inconsistent or poor social relating in a child expected to be ‘charming’ or ‘outgoing’ may create some frustration for all concerned and may lead to a poor fit between the child and the expectations in the environment.”[iii]

Parents, many of whom report that the symptoms associated with autism are more difficult to deal with than Down syndrome, can feel that their child’s slower development is their fault; that they haven’t done enough to help their child with Down syndrome. They notice that other children with Down syndrome are more advanced and exhibiting less severe behavioural problems, leading to feelings of frustration and inadequacy. These parents need extra support, but they may not feel like they fit in well with other Down syndrome families.

Beyond this, there is the practical matter of funding for therapy services. In British Columbia, a Down syndrome diagnosis does not give families access to funding for intervention, even though all children with Down syndrome can benefit from speech therapy, occupational therapy, specialized education services, and more.

On the other hand, the autism diagnosis opens the door to a significant amount of funding for such services: $22,000 per year through age five, and $6,000 per year from ages 6-18. The delayed autism diagnosis for children with Down syndrome, then, results in them receiving far less therapy than those with autism alone, despite facing double the challenges. All told, a child diagnosed at three will receive $144,000 for therapy and supports throughout their childhood. A child with Down syndrome who is diagnosed with autism at 14 will receive $30,000 – all of it coming after their most crucial developmental years have passed. It’s not about the money, it’s about the lost opportunity to build skills necessary for independence.

Why is Diagnosis So Difficult?

Unlike Down syndrome, which is conclusively diagnosed via a simple blood test, Autism Spectrum Disorder is a subjective diagnosis based upon observed behaviours and social communication patterns. In order to be diagnosed with autism, a person must meet all four of the following criteria:

A: Persistent deficits in social communication and social interaction across contexts, not accounted for by general developmental delays, and manifest by all three of the following: social and emotional reciprocity, nonverbal communication behaviours, and developing and maintaining relationships

B: Restricted, repetitive patterns of behaviour, interests, or activities as manifested by at least two of the following: stereotyped or repetitive speech or movements, excessive adherence to routines, highly restricted/fixated interests, hypo- or hyper-reactivity to sensory input

C: Symptoms must be present in early childhood

D: Symptoms together limit and impair everyday functioning

Parents of children with both Down syndrome and autism will often say that they “knew something was different.” It’s often just a matter of degrees, because part of what makes autism so difficult to identify in children with Down syndrome is that many of the characteristics are common to both conditions, particularly in the area of communication. And, although there are a lot of bits and pieces that make up autism, it is primarily a disorder of social communication.

Students with DS can have challenges in almost every area of speech and language development, including:

  • Underlying cognitive skills
  • Expressive language
  • Speech sound production/general intelligibility
  • Stuttering
  • Voice

Social communication is an area of increasing concern among students with Down syndrome. Early in life, many young children with Down syndrome have trouble with differentiating emotions shown on the face, taking turns, interacting appropriately with peers, and greetings. Later, children may continue to have difficulty with eye contact and greetings, and earlier deficits in turn-taking now surface as inappropriate conversational behaviour (asking partner-directed questions, topic maintenance, elaboration of topic, etc.). Still older children and adults with Down syndrome may have trouble repairing communication breakdowns.

If you think this all sounds like autism, you’re right! That’s part of what makes dual diagnosis so tricky.

On the other hand, despite these shared characteristics, there are other traits common to children with Down syndrome that may seem incompatible with autism. It’s a stereotype, yes, but it’s a stereotype because there is some element of truth to it: many people with Down syndrome do have a perceived strength in social abilities. While children with Down syndrome are often seen as friendly and sociable, children with autism can present as socially impaired, aloof and isolative. What we’re learning, however, is that children with both Down syndrome and autism may actually be more social than children with autism alone.

Yet another obstacle to an accurate diagnosis is the nature of the testing itself. The assessment team consists of the same professionals who diagnose any child with autism, which may include a developmental psychologist or psychiatrist, paediatrician, and/or a speech-language pathologist. They use the same assessment measures that are used with all other children who are suspected of having autism. This creates measurement issues with kids who are nonverbal or low-verbal, and/or severely intellectually impaired.[iv]

Formally assessing a child with a developmental disability using a standardized test is incredibly difficult – not to mention extremely discouraging for parents who have to see their child’s scores plotted at the very bottom of the chart. The child may have difficulty with the test due to overall low functioning, poor attending skills, high variability from day to day, environmental factors, or challenging behaviours. Many studies have noted the tendency for autism to be more commonly diagnosed in children with Down syndrome who are functioning at a lower cognitive level.[v]

This is where a lot of challenge with assessment arises: Does a failure to show a particular communication or social skill arise due to an overall low level of intellectual functioning, or is it because of a specific, qualitative deficit?[vi]

Nevertheless, it is possible to tease apart low intellectual functioning and autism. Several studies and researchers in this area refer to an “autistic flavour,” “autistic quality,” or “autistic-like condition” rather than clear-cut criteria.[vii] Assessors have mentioned that their final decision is a “gut” one. It’s far from ideal, but this is the current reality.

What to Watch For

We are often asked by parents whether we think their child may have autism, or whether they should be assessed. We have broken down the most common warning signs into two categories: grey flags and red flags.

Grey Flags

With regard to these grey area characteristics, a good rule of thumb is not to worry about isolated items from this list, as these behaviours are relatively common for children with Down syndrome alone. However, the more you see from this list, the more concern you might develop.

  • prefers sameness; insists on routines (must remember degree here – there is a difference between a general preference for sameness and a rigid insistence that significantly disrupts life on a daily basis); note: this is also a characteristic of OCD
  • does not hear very well, and as a result, does not always respond to their name, or to questions and directions
  • has limited expressive language; and/or uses some stereotyped, repetitive utterances
  • has poor eye contact
  • has sensory issues (e.g. finicky eaters)
  • engages in some repetitive play
  • mouths objects
  • has restricted interests
  • has challenging behaviours
  • slower than normal (for Down syndrome) development (i.e. functioning in the moderate to severe range of intellectual disability)
  • anxiety
  • repetitive, stereotyped behaviours[viii]
  • social communication issues such as: limited perspective-taking ability or limited reciprocal conversation ability

Red Flags

The red flag characteristics are more concerning, as these behaviours are not typically associated with children who just have Down syndrome.

  • no interest in communicating with others (i.e. social indifference/withdrawal)
  • general lack of interest in people
  • no use of gestures
  • regression in cognitive, language, and/or social abilities
  • total lack of verbal communication, coupled with no attempts at using other modes
  • Treating people as inanimate objects i.e. using someone’s hand to get desired object[ix]
  • ‘Odd’ behaviours sometimes associated with autism (e.g. smelling objects) or self-injurious behaviours

What to Do if You Suspect Autism

If you suspect your child may have autism, the first step is to consult with one or more members of your professional support team, such as your pediatrician, speech therapist, or child psychologist. If they share your concerns, they can provide you with a referral for a formal assessment.

For many parents, another label for their child (and another long series of assessments) is the last thing they want, and that is totally understandable. However, an accurate diagnosis is important for truly understanding your child and getting the best possible support to help them achieve their fullest potential – whatever that may look like.

Whether your child has one diagnosis, or two, or many, their conditions do not define them. They are who they are, in all their strengths, challenges, and quirks of personality. Or as Becca (who hates it when anyone calls her by anything other than her name) says, “I’m not (sweetie/honey/beautiful/sister/daughter/Down syndrome/autism), I’m just Becca!” That she is… and Becca is awesome.



[i] Capone, G. T., Grados, M. A., Kaufmann, W. E., Bernad‐Ripoll, S., & Jewell, A. (2005). Down syndrome and comorbid autism‐spectrum disorder: Characterization using the aberrant behavior checklist. American journal of medical genetics Part A134(4), 373-380.

[ii] Rasmussen, P., Börjesson, O., Wentz, E., & Gillberg, C. (2001). Autistic disorders in Down syndrome: background factors and clinical correlates. Developmental medicine and child neurology43(11), 750-754.

[iii] Howlin, P., Wing, L., & Gould, J. (1995). The recognition of autism in children with Down syndrome‐implications for intervention and some speculations about pathology. Developmental Medicine & Child Neurology37(5), 406-414.

[iv] (Capone et al. 2005)

[v] (Capone et al. 2005)

[vi] Starr, E. M., Berument, S. K., Tomlins, M., Papanikolaou, K., & Rutter, M. (2005). Brief report: autism in individuals with Down syndrome. Journal of autism and developmental disorders35(5), 665-673.

[vii] (Capone et al, 2005; Starr et al. 2005)

[viii] Capone, G., Goyal, P., Ares, W., & Lannigan, E. (2006, August). Neurobehavioral disorders in children, adolescents, and young adults with Down syndrome. In American Journal of Medical Genetics Part C: Seminars in Medical Genetics (Vol. 142, No. 3, pp. 158-172). Hoboken: Wiley Subscription Services, Inc., A Wiley Company.

[ix] Ghaziuddin, M., Tsai, L. Y., & Ghaziuddin, N. (1992). Autism in Down’s syndrome: presentation and diagnosis. Journal of Intellectual Disability Research36(5), 449-456.