Autism in theFamily - more common than we thought
This
morning I read a striking a new study which addressed the
question of autism in siblings – how common is it? The findings will be of vital interest to
many; most especially young families with an autistic infant.
Earlier studies and “conventional wisdom” suggested the
incidence of autism in siblings was in the 3-10% range. This new study shows those numbers to be very
far from the mark.
Scientists in this new study found autism in 19 percent of the younger
siblings. High as that seems the incidence is even higher in families with two or more autistic kids. In that case, a new sibling’s chances of
being autistic rose to more than 32 percent.
Being a boy makes a difference too. “Only” 9% of girl siblings were autistic, as
compared to 26% of boys. I found this
difference quite interesting because I often wonder if autism is
under-diagnosed in females. In this
study, all the kids were screened with the gold-standard ADOS or ADIR tests
prior to age three. So even with
top-notch screening, we still have more autistic boys.
Those are some strikingly high percentages. As high as they are, and knowing autism is a
spectrum condition, I have to wonder how many non-diagnosed siblings will
eventually turn out to have less severe but still noticeable “differences.”
There were a few more points I found interesting. First of all, the IQ of the child did not
predict anything. Neither did severity
of autism, as defined by the ADOS diagnostic scales. So your odds of having a second autistic kid
are higher, but those odds and knowledge of the first kid don’t combine to give
any insight into how a second kid might end up.
The conclusion is inescapable:
autism does run in families.
According to these findings, the more autistic kids you have, the more
you are likely to keep having.
We talk about autism having both genetic and environmental
components. This study, with 664 infants
distributed all over the country, shows a very powerful genetic component. That certainly does not diminish the role of
environment, but it’s sobering.
I predict the results of this study will have a profound impact
on family planning, because it casts parents’ chances of having a second or
third child with autism in a strikingly different light that any previous study.
We already know (from other studies) that many parents stop
having children when their first child receives an ASD diagnosis. This new finding may significantly reinforce
that tendency.
Read the study yourself at this link
The study involved 664 infants from 12 U.S. and Canadian
sites, evaluated as early as 6 months of age and followed until age 36 months. Kids with previously identified autism-related
genetic factors such as Fragile X were excluded from the study group
“It's
important to recognize that these are estimates that are averaged across all of
the families. So, for some families, the risk will be greater than 18.7
percent, and for other families it would be less than 18.7 percent,” said Sally
Ozonoff, Ph.D., professor of psychiatry and behavioral sciences at the MIND
Institute and the study's lead author. “At the present time, unfortunately, we
do not know how to estimate an individual family's actual risk.”
This
study was based on data from the Autism Speaks High Risk Baby Siblings Research
Consortium (BSRC) and led by investigators from the UC Davis MIND Institute.
Your
correspondent (John Elder Robison) is a member of the Science Board of Autism
Speaks, one of the organizations who funded the work.
Comments
Why?
Also, I have always assumed a strong genetic component-- having AS myself, and sharing the traits with my daughter, my father, and other family members like my cousins. I have always wondered whether it occurs in some ethnic groups more than others (being from a Scottish, Irish, and German background). But, I have been told there is no evidence of this.
I don't have a turtle... so, I can not answer for that.
I write as someone with a 7 and three-quarters hat size.