Autism Baby Siblings Study: recurrence risk 19%

15 Aug

Results of the MIND Institute’s baby sibling study have been published in the journal Pediatrics. The study puts the recurrence risk of autism at 19%. In other words, a family with one autistic child has, on average, a 19% chance that a subsequent child will be autistic. The study authors stress that the risk may be higher in some families and lower in others.

More discussion can be found in various news outlets carrying the story, including

10 Responses to “Autism Baby Siblings Study: recurrence risk 19%”

  1. Vincent Iannelli, MD August 15, 2011 at 18:42 #

    Since it often seems like many parents of children with autism can be less likely to vaccinate subsequent children, what does a higher rate of autism in a group of children who are less likely to be vaccinated mean for the anti-vax groups?

    • Sullivan August 15, 2011 at 23:13 #

      Vincent Iannelli, MD,

      Since it often seems like many parents of children with autism can be less likely to vaccinate subsequent children, what does a higher rate of autism in a group of children who are less likely to be vaccinated mean for the anti-vax groups?

      As I believe you are aware, there was a study presented at IMFAR looking at vaccines and autism risk. One line from the abstract:

      Instead, because siblings of children with autism were less likely to be vaccinated according to the recommended schedule, both correlations and multiple regressions revealed a significant relationship between higher rates of vaccination and non-ASD behavioral outcomes.

      Not published or peer reviewed as yet. But, an interesting observation.

  2. vmgillen August 15, 2011 at 19:17 #

    “subsequent children more likely to develop autistic traits…” Let me tell you about my daughter (Dx: Downs; social skills through the roof), sibling of a young man with very involved, we-ain’t-kidding autism, who was running ABA programs in her school in 2d grade; who wanted to get out of her class in middle school and convinced her teachers she had serious ASD… here, again, we see the problems presented by lack of etiology.

  3. Liz Ditz August 15, 2011 at 20:36 #

    Dear Dr. Iannelli, first of all the ardent “autism is vaccine injury” folk have already expressed dissatisfaction with this study as “a waste of money” and “another way to blame parents”.

    Secondly, I challenge your assertion that “many parents…less likely to vaccinate”. It’s anecdata, but in our local special education PTA, every single child with autism is fully vaccinated. We just don’t have any current “autism is vaccine injury” parents (although we have a few reformed parents). The “autism is vaccine injury” group just has a big, well-funded soapbox and megaphone.

  4. Vincent Iannelli, MD August 15, 2011 at 20:48 #

    “Secondly, I challenge your assertion that “many parents…less likely to vaccinate”.”

    Well, part of that is based on personal experience.

    But there was also an ongoing study, the results that were partially published in Pediatrics in 2008 as a letter to the editor that supported that idea.

    “Immunization Uptake in Siblings of Children With Autism”

    In the course of conducting a prospective study of siblings of children with autism, we have observed a disturbing trend of reduced uptake of immunization for the younger siblings.

    I have tried to contact them to see if they ever finished the study.

  5. Liz Ditz August 15, 2011 at 20:54 #

    Kristina Chew on the study

    Frankly, I wasn’t really surprised to learn about the higher rates of autism found in younger siblings of autistic children in the new Pediatrics study, nor was my husband. We’ve long thought the estimates of 3 to 10 percent were low and know several families with more than on autistic child. In some cases, the children’s autism diagnoses are at different levels of severity on the autism spectrum (one child might have Asperger’s and the other autism; the child with Asperger’s might only have been diagnosed after their younger sibling was diagnosed).

    She brings up a good point, which is did the family undertake a subsequent pregnancy before or after the older sibling’s autism was diagnosed?

    And another point: many people (myself among them) sort of assume that all pregnancies are planned. However, fertility and birth control are chancy things. I know at least three families where the child born after the child with autism were not exactly intended.

  6. RAJ August 15, 2011 at 23:19 #

    Autism is associated with birth complications so the recurrance risk shouldn’t be any great surprise. Autism is been shown in several studies to be associated with pre term birth and pre-eclampsia for example;

    Recurrance risks for pre-term delivery is highest (57%) in women with two prior pre term deliveries. Recurrence risk, which is affected by the frequency, order, and severity of prior preterm births with a 57% recurrance risk for women with 2 prior very preterm deliveries (21-31 weeks).

    The risk of recurrent preeclampsia in pregnancy is inversely related to gestational age at the first delivery: 38.6% for 28 weeks’ gestation or earlier, 29.1% for 29-32 weeks, 21.9% for 33-36 weeks, and 12.9% for 37 weeks or more.

    Familial autoimmune disorders which can be transmitted to the fetus in pregnancy is also associated with very high risk for autism and high recurrance risks. Pregnancy problems associated with maternal auto-immune disease include prenatal maternal urinary tract, upper respiratory, and vaginal infections and in the newborns asphyxia; prematurity, and seizures are more common in the autistic group.

  7. sharon August 15, 2011 at 23:33 #

    AS Liz and Kristina point out the previous stats on this seemed to me to be quite low based on personal observations.

    The idea that pointing to genetic probabilities is ‘blaming the parents’ is ludicrous. But the claim this study was a waste of money? Why, because it was less dollars spent trying to prove a dead in the water theory about vaccines or mercury?

  8. Samantha Pierce August 16, 2011 at 20:42 #

    I had always been under the impression that the recurrence rate was 20%. That’s the number I was aware of when my husband and I chose to have more children. We didn’t find autism as scary as some people seem to. To me this study feels like I’m being told something I already figured out for myself years ago.


  1. Immunization uptake in younger siblings of children with autism spectrum disorder « Left Brain Right Brain - October 12, 2012

    […] Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study and discussions here and elsewhere). Anecdotally, we hear a lot about families deciding to forgo or delay vaccines after […]

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