News The latest developments in autism research.

Clinical research: Down syndrome, autism often coexist

by  /  27 June 2014

Regression risk: Children who have both autism and Down syndrome are more likely to lose language and other skills than children who have Down syndrome alone.

Nearly 40 percent of people with Down syndrome also meet the criteria for an autism spectrum disorder, suggests a U.K. study of nearly 500 children, published in Autism Research1.

The study found that 38 percent of children with Down syndrome meet a screening test cutoff for either classic autism or another pervasive development disorder on the autism spectrum.

In keeping with the elevated prevalence of autism in males, the study shows that boys with Down syndrome are significantly more likely to meet the criteria for an autism spectrum disorder than girls with Down syndrome.

The study assessed whether children show signs of autism by asking their caregivers to fill out the SocialCommunication Questionnaire (SCQ), which consists of yes-or-no questions about social and communicative deficits and repetitive and restricted behaviors.

The researchers note that the SCQ does not provide a clinical diagnosis. For example, using the SCQ and an additional questionnaire, a 2010 study initially estimated that 42 percent of children with Down syndrome have an autism spectrum disorder. However, after assessing some participants using more rigorous in-person tests, it downgraded the estimate to 18 percent2.

Two other small studies that relied solely on the SCQ also yielded relatively low numbers, estimating that between 16 and 19 percent of children with Down syndrome have autism3, 4.

The researchers who led the new study say their own estimates may be high because their relatively young sample includes parents with a heightened awareness of autism. Down syndrome’s overlap with autism has also become better known in recent years.

The new study compared children with Down syndrome who meet the cutoff for an autism spectrum disorder with another group of people with autism spectrum disorders who were assessed in a 1999 study5.The children who have both disorders are more likely to have trouble with small talk and to engage in compulsions and rituals than are children with autism alone. And they are more likely to be to be hyperactive and to have emotional and behavioral problems than children with Down syndrome alone. They are also more likely to have lost language abilities and other skills they had previously gained than children with Down syndrome alone.

However, they tend to be better at making social overtures and responding to other children who approach them than are those with only autism.

Given these distinctions, the researchers say, people with the dual diagnoses may benefit from specialized treatment plans.


1. Warner G. et al. Autism Res. Epub ahead of print (2014) PubMed

2. DiGuiseppi C. et al. J. Dev. Behav. Pediatr. 31, 181-191 (2010) PubMed

3. Lowenthal R. et al. J. Autism Dev. Disord. 37, 1394-1395 (2007) PubMed

4. Moss J. et al. Autism 17, 390-404 (2013) PubMed

5. Berument S.K. et al. Br. J. Psychiatry 175, 444-451 (1999) PubMed

11 responses to “Clinical research: Down syndrome, autism often coexist”

  1. alanpacker says:

    It’s worth noting that the chromosome 21 gene DYRK1A, which is thought to be a critical factor in the cognitive deficits observed in Down syndrome, is now firmly established as an autism risk gene. It has a documented role in regulating overall brain size and excitation-inhibition balance, and it may be that altered DYRK1A dosage in either direction increases susceptibility to autism–in the context of Down syndrome if there’s too much DYRK1A, and in idiopathic autism if there’s too little. As such, research to identify small molecules that modulate DYRK1A expression or function may prove to be useful in treating both conditions.

  2. RAJensen says:

    In studies of Down Syndrome and co-occuring autism using the strict criteria of DSM-IV or ICD-10 have found the co-occurance rate is about 6-7%, This study used the SCQ screening tool and did not have a general population control group. The SCQ tool shows autistic traits are present and widely distributed throughout the general population.Typical of the tools like the SRS and ASQ which have been consistently shown to overdiagnosis ASD

  3. Suzann Armitage says:

    I wonder what the study would show with the new diagnostic criteria. While I have seen children with autism and Down syndrome, I think the 40% figure is high.

  4. Karen Gavin says:

    I have a 16 year son with dual diagnosis and a severe learning difficulty. I don’t think the 40% figure is too high at all given the other children we know also with both DS and ASD. These children fall between 2 stools; they are not like children just with DS and they are not like children just with ASD, so anything you read, about the single diagnosis, which is helpful to parents for teaching and learning does not seem to apply to children with both DS and ASD. They certainly do need a teaching approach specifically designed for them.

  5. Loes van Doorn says:

    I also have a son with both DS and PDD-NOS. But here in Holland we don’t get special teaching approach. He is almost 16 years old now, and still not able to express himself. I thought he had autism already when he was a very small boy, but the doctors told me I was crazy! It was only 5 years ago that they found out he had PDD-NOS. I wish there was a solution for him to learn to talk because he is very smart, but no language abilty…

  6. Anonymous says:

    I have a adopted child with Downsydrow Can u tell me when they talk!”she just started to walk an she 2!can u give me details on things I need to know”””

  7. Monique says:

    Hello, I have a daughter with a dual diagnosis, she is 13 now she was born with Down Syndrome. She has always had Autistic tendencies. Her therapist would often say it and I also knew she was different even from her Down Syndrome peers. I had her evaluated for Autism at 7 years old, and she has middle of the spectrum Autistic disorder. It is very unique to her having a dual diagnosis. It is like she has the best of both if there is such a thing. She has the sweetness and hugs of DS and the aloofness of Autism. Too long to explain here. I just know she is a person with a one tract mind who will love you to pieces, then want to put you back together again.

    • Omar's mom says:

      Hi Rigina, do you have an email address ? I would like to email you please. I have a boy with Down syndrome and I’m thinking might be autistic to. Can you please help by answering a few questions? Thank you

  8. Regina says:

    I also have a daughter with DS-ASD. She is 24. Diagnosis was made at age 16. I wish we had received the diagnosis sooner. Her IEP would have been completely different. We definitely experienced the regression of communication skills, lack of eye contact, and the development of repetitive behaviors.

  9. Regina says:

    I have a son with a dual dx of autism/Down Syndrome. He was diagnosed at 14.
    He is now 22 years old and just starting to communicate verbally. he is not like people with down syndrome and not like people with autism. He was diagnosed by Johns Hopkins and the dx was very clear. This diagnosis is not as old as people think and we were struggling to have this diagnosis given to us. It made all the difference in his development to obtain this diagnosis within a school setting. We felt the bias towards him and our family for years as to why he was not developing as a child with Down Syndrome should. There can be lots of psychological damage to families and bias towards them if this dx is not obtained. Happy that society is going forward and becoming open to dxs of autism..Praise the Lord!

  10. Maria says:

    I think this rate is not far from reality. Kids with Downs syndrome are at a higher risk for Autism because they often has sensory issues that can lead to Autism. They also have mitochondrial dysfunction that it is not diagnosed. If a parent of a child with Down syndrome try to get the diagnosed, the doctors shot the door on your face. Almost 100% of kids with Down syndrome have mitochondrial dysfunction, which is easy to spot because most of kids with Down syndrome have hypotonia (low muscle tone). About 80% of kids with Autism somehow have Mitochondrial dysfunction as well. This is what says about Autism and related diseases:

    (Shoffner, JM et al. J Child Neurol. 2010 Apr;25(4):429-34; Epub 2009 Sep 22) The most common clinical observation in children with both ASD and mitochondria disorder was hypotonia, or muscles with low tone, followed closely by “fatigue with activity.” They also found that approximately 60 percent (17 of 28) of these children experienced a regressive form of ASD, a rate of regression that is over two times greater than what is observed in the general population of individuals with ASD.

    The answer is in science research, but everybody is looking and reading the same page.

Leave a Reply

Your email address will not be published. Required fields are marked *