Autism Spectrum Disorder


Autism spectrum disorder occurs more often in children with Down syndrome than in other children. Prevalence may be as high as 10. The dual diagnosis of autism and Down Syndrome can be extremely disabling.

Children with Down syndrome, who also have the dual diagnosis of an autistic spectrum disorder, tend to receive a diagnosis at an older age than their peers. Their parents and carers may experience a long wait and considerable difficulty in obtaining the diagnosis .


There is often reluctance to consider the possibility of co-existent Down syndrome and Autism spectrum disorder (ASD.) There are several reasons why the diagnosis is frequently much delayed, including:

  • the belief that children with Down syndrome are always ‘sociable’ and friendly, so cannot be ‘autistic,’
  • the complexity of diagnosis of neurodevelopmental disorders in association with significant developmental delay
  • communication difficulties thought to be due primarily to be due to delay of speech and language
  • lack of awareness of the usual developmental profile of children with Down syndrome.


There are a number of recognised risk factors for autism, in children with Down Syndrome. These include:

  • Seizures, particularly West syndrome (infantile spasms)
  • Early Hypothyroidism
  • Post cardiac surgery complications
  • Severe learning difficulties/ lower IQ
  • First or second degree relatives with the autism phenotype

Children may display behaviours typical of autism in infancy or as toddlers, and follow a course similar to that seen in other children. However it is not unusual for the condition to be heralded by regression of social and communication skills noted in later childhood.

The possibility of Autism spectrum disorder must be considered in any preschool child with Down syndrome who is failing to make expected progress in speech and language, social communication and social interaction skills, and in any older child who shows regression of these skills.

There are a number of important conditions to consider in evaluating a possible dual diagnosis of autism and Down Syndrome. These are more common in Down Syndrome and may cause diagnostic confusion or increased disability. These include:

– Hearing impairment

– Visual impairment

– Hypothyroidism

– Major concurrent illness

– Profound and severe multiple physical disability

– Severe learning difficulties

– Social deprivation/neglect

– Attachment disorders


– Mood disorders.

Diagnosis is critically important because when the two conditions coexist autistic disorder takes precedence in terms of educational and management needs.


Presentations at DSMIG Meetings

Materials from this meeting are available for members only who need to log in to access them. For details on how to become a member click here.


Additional Resources

Autistic Disorder and Down’s syndrome Dr Jennifer Dennis .Down’s syndrome association Journal no.128 (2013)


Autism and Down syndrome Professor Sue Buckley. Down syndrome news and updates (2005 )


Autism spectrum condition, complex needs and visual resources

Understanding dual diagnosis of Down’s syndrome and autism spectrum condition training days for parents and professionals through DSA.Gillian Bird, Down Syndrome Association Training Services Manager


Autistic-Spectrum Disorders in Down Syndrome:Further Delineation and Distinction from Other Behavioral Abnormalities

John C. Carter,George T. Capone, Robert M. Gray,Christiane S. Cox,and Walter E. Kaufmann, American Journal of Medical Genetics Part B (Neuropsychiatric Genetics) 9999:1 7 (2006)


Down’s syndrome and autistic spectrum disorder: a look at what we know.  Capone G. (2001) NDSS website


The recognition of autism in children with Down syndrome: implications for intervention and some speculations about pathology.Howlin P, Wing L, Gould J (1995) Dev Med and Ch Neurol. 37 406-414


Autistic disorders in Down’s syndrome: background factors and clinical correlates.  Rasmussen P, Borjesson O, Wentz E, Gillberg C. (2001)Dev,Med, Ch,Neurol. 43 750-754


Book Chapter

Developmental, Psychological and Psychiatric Function. Jeremy Turk

Down Syndrome – Current Perspectives MacKeith 2015
ds-current-perspectives-book-coverEdited by Richard Newton , Shiela Puri and Liz Marder