However, there is increasing evidence that children with Down syndrome can have a “dual diagnosis” which means they also have autism or have a disorder on what is referred to as the autism spectrum.
Down syndrome is a genetic condition that is caused by a chemical interaction between the egg and the sperm. It results in each cell of the embryo having an extra chromosome (47 instead of 46). As cell composition affects how humans develop, the extra chromosome creates a comprehensive change to the body and brain of the baby, and they are born with the characteristics of Down Syndrome.
It is possible to test for Down Syndrome at various stages during the pregnancy, so many cases are now identified this way. However, the profound impact of this condition, including distinctive facial features, means it is easy to detect at birth too.
This means it is extremely rare for Down Syndrome to be diagnosed at a later point in the child’s development.
A diagnosis of autism is far more challenging, not least as the developmental and behavior issues it encompasses can appear singularly in children at any point in their early years. As a result, there is a huge debate over how many children and adults in the USA have this medical condition.
Its cause is unknown and there is currently no blood test or scan that can detect this condition. It is identified using three different measurements.
For there to be a diagnosis of autism, all three of these criteria would need to be met, at a significant level. It is possible to be high functioning, even highly intellectual, and still have a diagnosis across these three measurements.
A child with one or two of these, or mild issues with all three, is more likely to be classified as having “autistic spectrum disorder”, which puts them on a sliding scale of severity. Recently, Asperger's Syndrome has been added to the autistic spectrum, a developmental disorder that affects how a child perceives the world, and their relationship with other people.
Physicians generally believe autism becomes diagnosable at three years old. One of the reasons it is hard to identify is that children with learning difficulties, problems with hearing and speech, or those with some form of brain damage may appear to meet the criteria on the autism symptom list.
Making a dual diagnosis of these conditions is extremely challenging. It is only in the last 25 years that Down Syndrome vs autism has been studied to find common ground.
Studies in the UK and Sweden have suggested that approximately 5 to 7% of children with Down Syndrome have autistic spectrum disorders. A small, but significant amount.
If a child with Down Syndrome begins to show behaviors and development problems that are also inherent in autism spectrum disorder, naturally caregivers will want medical confirmation that there is a second issue to consider.
However, Down Syndrome brings with it learning difficulties, which may impede social and communication skills. This, in turn, may cause the child to become obsessive in certain behaviors.
Sifting through this sufficient evidence of a separate diagnosis is complex, but important. The awareness that the child also has autism will ensure that they receive the right level of help and educational support.
It is also possible that conditions that can arise from Down Syndrome - such as infantile spasms, epilepsy, brain damage during heart surgery, severe persistent infections or profound hearing or visual impairments - can also lead to a child developing autistic traits.
Specialists in this field have expressed concern that it is possible to over diagnose autism in children with Down Syndrome, leading them to be categorized and directed in an inappropriate way. It could be that they don’t receive the educational opportunities they would benefit from, due to misdiagnosis.
This suggests that it would be advisable to observe communication, social interaction and repetitive behaviors over time, to ensure that the criteria for an autism diagnosis are consistently met.
As indicated, a correlation between Down syndrome and autism has not been meaningfully explored yet in terms of either medicine or education.
A great deal more research is required to study clinical evaluations and to create unequitable psychological and behavioral testing.
This can then ensure that a dual diagnosis is not missed, or issued inappropriately.