Recurrence of autism in siblings

It is a question that I'd imagine most paediatricians or related healthcare professionals get asked a lot when it comes to the autism spectrum conditions: "my child has autism, what is the risk that any future siblings might also develop the condition?"

Sisters @ Wikipedia 

Indeed, whole initiatives have been formed to build on the fact that the appearance of offspring autism does seem to carry an enhanced risk of other siblings also presenting on the spectrum* (open-access) as per the Autism Speaks High Risk Baby Siblings Research Consortium (BSRC). That being said, if your first language is not English when living in an English-speaking country, you might not necessarily get a prompt diagnosis (see here).

To add to the growing scientific literature on this topic, the recent paper by Therese Grønborg and colleagues** is the topic of today's post and their assertion that depending on whether brothers or sisters are full siblings and their birth year, the risk of recurrence of an autism spectrum disorder (ASD) varied between about 4% and 10% in Denmark, quite a bit higher than the Danish population prevalence of just over 1% (or even more?) but itself probably an under-estimate given the issue of stoppage. Jon Brock over at Cracking the Enigma is quoted on some analysis of these results (see here). Indeed, the headline which quite a few press elements have picked up on is that the "overall relative recurrence risk for ASDs was 6.9" equating to a nearly 7-fold increased risk of autism if an older siblings has been diagnosed with ASD.

OK, I know that this is not new news. That more than one child in the same family might have autism is a reality that many, many families have experienced. Science has been talking a long time about the heritability of autism (and the broader phenotype) from quite a few perspectives; even though genes are probably not working in isolation (see this archive post) alongside that new Sheriff in town called epigenetics (see here). Another important issue taken up from this recent paper outside of the disparity between this population-based study and other more clinical samples - the estimates from the Grønborg paper are lower than that found in other studies - is how those just-as-important half siblings seem to indicate other potential issues also being pertinent areas for further investigation (think the nine months that made us and things like folate even the folding placenta for example).

There is always a need for this kind of basic science in autism circles not only for research purposes but also to inform families about risk (bearing in mind that risk is risk) and potentially inform services such as education and health as a function of things like heightened comorbidity too (see here). Indeed if I had to add anything to this area of investigation it would be to include autism as part of a wider suite of conditions/characteristics which may very well be noted in other siblings (see here) as per some other interesting work with its roots quite a few moons ago (see here).

And just in case you need it, here is a nice article from the BBC about the value of having siblings.

[Update September 2013: The full text of the Grønborg paper is available here].

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* Ozonoff S. et al. Recurrence risk for autism spectrum disorders: a Baby Siblings Research Consortium study. Pediatrics. 2011 Sep;128(3):e488-95. doi: 10.1542/peds.2010-2825. Epub 2011 Aug 15.

** Grønborg TK. et al. Recurrence of Autism Spectrum Disorders in Full- and Half-Siblings and Trends Over Time A Population-Based Cohort Study. JAMA Pediatr. 2013;():-. doi:10.1001/jamapediatrics.2013.2259

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Grønborg TK (2013). Recurrence of Autism Spectrum Disorders in Full- and Half-Siblings and Trends Over Time A Population-Based Cohort Study JAMA Pediatrics DOI: 10.1001/jamapediatrics.2013.2259