Sunday, 30 March 2014

2 Studies: Why Autism is More Prevalent in Boy and Siblings of Children With Autism

Initially I was going to do this as two posts but decided I would combine them.

I found two studies on autism this week on the Sensory Spectrum.

The first was a study on why autism is more prevalent in boys than girls.

Sebastien Jacquemont at the University Hospital of Lausanne did comparisons of boys and girls diagnosed with autism.  To catch everyone up, boys are diagnosed with autism at a rate of 4 to 1 compared to girls.  And there is significantly lower number of "high-functioning" girls compared to high-functioning boys, so girls who are diagnosed tend to more severe.

There have been a number of suggestions as to why this is.  Do the high-functioning girls get more inadvertent behaviour therapy as girls are often encouraged to pay more attention to other people's feelings anyway?  Do girls actually have some sort of protection by being more statistically empathic?  Are parents and doctors simply more likely to notice a problem in a boy before a girl?

Mr. Jacquemont (he's not identified as a doctor in the article) found that girls who are diagnosed had a "greater number of harmful CNVs than did males diagnosed with the same disorder."  (CNVs are copy-number variants, areas where a particular gene has been miscopied from cell to cell.)  He tells us his findings "suggest the female brain requires more extreme genetic alterations than does the male brain to produce symptoms of ASD."

This does suggest something genetic but doesn't actually address the underlying question.  To do that, he would have to see if he could find girls with low numbers of CNVs (comparable to the low-level boys) and test to see if they qualified for high-functioning autism.  If the girls are out there, but unidentified, then autism isn't really gender specific.  If they aren't out there, then that would be a far more interesting development since it would almost definitively prove a gender-specific weakness and give us a much better understanding of how autism actually develops.  It would also suggest a strong genetic link, which might discredit the environmental folk (who claim vaccines or heavy metals are responsible).

The second was a study on how siblings of children with autism can show atypical development at 12 months.

We participated in such a study (although I don't think this is the same one).  Regular odds for having a child with autism are 1 in 80(ish).  With a sibling with autism, the odds drop to 1 in 20.  And many scientists think the number is low as parents often choose not to have another child after their child is diagnosed with autism.

The article implies that signs can be detected in siblings sooner than they can be detected in a first-born child or one with neuro-typical older siblings.  I'm not sure that is actually the case or if parents and doctors are simply looking closer and notice more subtle signs.  Or perhaps siblings really are showing signs earlier since they have an autistic model for their behaviour in their older sibling.

Either way, I applaud the recommendation that siblings be checked carefully and frequently once a child has been diagnosed with autism.  Parents should be made aware the odds are greater so they can make informed decisions.

No comments:

Post a Comment