The Similarities and Differences between Fragile X Syndrome and Autism
What are Fragile X Syndrome and Autism?
Fragile X Syndrome (FXS) is a condition with a known genetic cause, which can be identified with a blood test. Approximately 1 in 4000 men or boys, and 1 in 6000 girls or women have FXS. FXS is associated with a number of psychological and physical characteristics (Read more here).
Autism, on the other hand, is a description of a pattern of characteristics. These include difficulties with social interaction and communication, as well as restricted or repetitive interests or activities. Autism is diagnosed by evaluating patterns of behaviour. The exact causes of autism are still being researched, but a complex range of genetic and environmental factors are likely to be involved. The estimates of prevalence vary, but it is believed that approximately 1 in 100 people may have autism. You can read more about autism on the National Autistic Society Website
What is similar?
Many of the behaviours associated with FXS are autistic-like, such as: avoidance of eye contact, social withdrawal, communication difficulties and repetitive behaviours. About one third of people with FXS have enough of these characteristics to meet the criteria to be diagnosed with autism, as well as FXS. This proportion of people with FXS who have Autism accounts for approximately 2-6% of all cases of Autism, making FXS the most common, known single-gene cause of the condition.
What is different?
Firstly, it is important to note that not everyone with FXS has autism, though many will have at least some autistic-like behaviour.
Though much of the behaviour in FXS is autistic-like, there are differences in what is driving the behaviour. In FXS, inattention, hyperactivity and anxiety interfere with learning from, or participating in, social interaction, resulting in autistic-like behaviours. Furthermore, autistic characteristics FXS become more prominent when there are more severe learning difficulties. In comparison, one of the core issues in Autism is social interaction and the factors that lead to the autistic behaviours are believed to be more varied.
The following table helps to explain this by discussing several shared characteristics between FXS and Autism, and how they differ:
In addition, even when Autism is present with FXS, the pattern of symptoms may be subtly different than in Autism more generally. Namely, people with Autism who have FXS tend to be more socially responsive (for instance, show more social smiling) but show more repetitive behaviours, when compared to people with Autism who do not have FXS. Therefore, even when an individual is diagnosed with Autism as well as FXS, it is important to understand their genetic condition.
Why is it important to understand the similarities and differences?
Autism is becoming ever more widely recognised and there is a fast-growing amount of evidence about different interventions to improve people's quality of life, which the Fragile X community may be able to learn from.
However, it is important that people who have FXS get the right diagnosis. Firstly, having the correct diagnosis allows for better understanding of the difficulties that the individual may face, and the best way to intervene. For instance, FXS is also associated with particular learning styles, and understanding these can be beneficial when teaching new skills (See Our Education Booklet for further information). In addition, as FXS is an inherited condition, members of the immediate and wider family would benefit from genetic counselling if their relative is diagnosed. As a result, Professor Jeremy Turk (Consultant Child and Adolescent Psychiatrist & Fragile X Society Professional Advisor) recommends FXS testing for people showing autistic-like behaviour, particularly when they also have a learning disability.
This piece was written using information from the following sources:
Fragile X Syndrome and Autism: Common Developmental Pathways? by Kim Cornish, Jeremy Turk and Mark Levitas (2007)
The fragile X syndrome–autism comorbidity: what do we really know? by Len Abbeduto, Andrea McDuffie and Angela Thurman (2014)
FXS and ASD: Similar But Different . National Fragile X Foundation