More evidence shows autism raises risk for later siblings
August 15th, 2011
01:00 AM ET

More evidence shows autism raises risk for later siblings

It's already known that children with older siblings who have autism spectrum disorder or ASD, have a higher risk of developing the condition themselves,  and a new study in Pediatrics finds that risk is even higher than previously expected.

"We expected the rates to be significant, but not as high as we found," said Dr. Sally Ozonoff, lead author and vice chair for Research at the Department of Psychiatry and Behavioral Sciences at the UC Davis M.I.N.D. Institute. “We pretty much know genetics is a factor somewhere in the autism puzzle, but there may be other factors that work with the genetic makeup to cause the condition. We just don't know.

"The message we'd like to see come from the study is primary care physicians need to look at infants more closely when they are born to a family with children with ASD."

In the study, the largest of its kind, according to Ozonoff, researchers monitored 664 infants, registered with the Baby Siblings Research Consortium who either had an older biological brother or sister with ASD. They followed the little ones from infancy to 36 months. Previous studies estimated that the ASD recurrence risk in younger siblings was between 3% and 10%. But this study found that the overall risk was much higher, at 18.7% and even higher in families with more than one affected sibling – about 32.2%.

"This does not mean that every family who has a child with ASD will have a second child with ASD. It's just their risks are higher," noted Ozonoff. "And keep in mind we found that 80 percent of children with older siblings who had ASD never developed any signs of autism. It's just an indicator that parents and physicians need to be aware of."

Male babies experienced nearly three times the risk over female infants, 26% versus 9%. Age of parent, gender of the older sibling or birth orders were not predictors of the condition, meaning if the first child in the family does not have ASD, and the second child does, the risk percentages are still the same for the next child.

"I think you'll find that parents with children who have ASD will not be shocked by these finding," said Dr. Alycia Halladay, director of research for environmental sciences for Autism Speaks, an advocacy organization that heads up the Baby Siblings Research Consortium. "But the data does support the importance of monitoring infants from birth who have older brothers or sisters with ASD. Because recognizing autism at an early age is key to getting a child successful treatment"

Authors of the study suggest their findings could also impact future genetic screening and family planning decisions when it comes to parents of children with ASD. The knowledge of the risk could also lead to earlier observation and intervention for babies born into these particular families.

"This study just backs up what other data has been saying, even more so, " said Ozonoff. "But we'd like primary care professionals to be more aware of the risks for newborns with ASD siblings, so they can ask the pertinent questions to parents about the new sibling, such as 'Is he or she looking at you, learning to point, smiling?' All of these are important aspects of deciding whether a young child may have ASD."

soundoff (147 Responses)
  1. J. Christensen


    I have to disagree with you.

    I have a son with a genetic disease that is always fatal – cystic fibrosis. He knows he will die from cystic fibrosis. Despite having never drawn a "normal" breath of air, despite having to do respiratory therapy two, three, or four times a day, despite being hospitalized at least once a year, he still finds life to be worth living and I can't imagine my life without him. Our family might not have what others would consider to be a "normal" life. But our life is wonderful and precious to us.

    I asked him what he thought about people choosing not to have a second or third child after the first was born with cystic fibrosis. He said that he thinks those people are no better ethically than the people who decided that Jews shouldn't have a right to live. He said that no one has the right to limit the genetic diversity of humanity or to decide for another human being whether or not that human's life will be worth living. Ask somebody with ASD if they'd rather have never lived than to live with ASD.

    August 15, 2011 at 15:22 | Report abuse | Reply
  2. Arman Khodaei

    This is not surprising at all. I am 26 years old and have autism. I have seen families where everyone has autism. I actually run three autism groups. I have a website with a blog and a support group in Southern California. My blog is http://www.empoweringautism.com and my group meetings can be found here http://www.meetup.com/empoweringautism

    August 15, 2011 at 16:12 | Report abuse | Reply
  3. Hope

    The full text of the study is available for free at the Pediatrics website. I would recommend to everyone commenting that you go to the source rather than just relying on the information in this article.

    You can see what the study authors have identified as limitations of the study. One of the things that was a huge red flag for me was that they had notably different results (heterogenity) from the 12 sites in Canada and the U.S. that they collected data from. (I wonder where the highest and lowest rates were.)

    "There was variability across sites in ASD outcome rates, which may reflect geographic diversity, regional variation, and/or method differences." I guess it wasn't that important to the researchers to try to figure out what was causing the heterogenity. It would have been nice for the authors to include more data in the Pediatrics article.

    Also, I don't know if they are collecting vaccination history for the baby siblings. It would be very useful information to know if the unvaccinated baby siblings are having different outcomes than the vaccinated baby siblings.

    August 15, 2011 at 17:24 | Report abuse | Reply
    • vickyjack

      When are people, like yourself, going to realize that autism has absolutely nothing to do with being vaccinated? Nothing has been proven that having your child vaccinated puts them at risk of getting autism – or bringing it out – however, you want to term it. My son was not vaccinated until AFTER he was diagnosed with autism. How do you explain that? You put your child more at risk by them not getting vaccinated. But anyone that brings up the vaccination argument scares new parents into thinking that if they avoid vaccinations their child will not develop autism. What a bunch of bunk! It's genetic, plain and simple.

      August 15, 2011 at 17:54 | Report abuse |
    • Sandra

      Vaccinations don't make a difference, it was already ruled out. Remember Wakefield the scammer(tm)? Tried and convicted of fraud.

      August 16, 2011 at 01:41 | Report abuse |
    • Irk

      Please copy and paste this link in your browser:


      If your child is vaccinated with mercury-containing vaccines, you are poisoning your child and harming their neurological development. There may be genetic factors for some, but the affect of mercury on the brains of infants is well established.

      August 16, 2011 at 08:29 | Report abuse |
  4. LarryG2

    Stands to reason since many cases of autism is actually misdiagnosed behavior problems.

    August 15, 2011 at 18:43 | Report abuse | Reply
    • leeann

      I assume you have statistics to back that up.

      August 16, 2011 at 10:05 | Report abuse |
  5. Auntiegrav

    This is a useless story. Since many ASDs are not diagnosed until later, it is too late to do anything about the younger siblings (unless you are having 14 kids spread out over 18 years or so).
    Also, what are the recommended actions if one DOES have a child born with autism?
    Sterilization? Abortion? Birth control?
    Don't talk about how important the study is and then leave the rest of the story hanging out there as though it doesn't lead to consequences.

    August 15, 2011 at 22:29 | Report abuse | Reply
    • angela

      It's called science. Better understanding a phenomenon helps us better address it. How do you go from a scientific study to the endorsement of abortion?! I have two kids with autism and I appreciate all of the research being put into this growing problem. And as for Larry up there, my kids don't have undiagnosed behavior problems. They have autism.

      August 15, 2011 at 23:05 | Report abuse |
    • Steve1121

      Autism is generally diagnosed between 18mo and 4 years of age, enough time to screen/observe younger siblings for the disorder. In retrospect, many children have clear signs of autism at a much earlier age, many times by 9 months of age. Vaccines have now been proven not to be linked to autism; it's time we move on to study other possible causes.

      August 15, 2011 at 23:23 | Report abuse |
  6. Frank

    Animals don't have ASD: they don't eat what we eat and are not exposed to as much chemicals. Similarly, I was suprised that a co-worker's dog died of cancer. He's a smoker and fed his dog with food from the table 100% of the time. The smaller body is affected faster. Just an obervation.

    August 15, 2011 at 22:45 | Report abuse | Reply
  7. Jayleen

    The article is worth the read but not conclusive in my opinion. I tend to think it is environmental. My guess is someday they will figure out that it is something, or a combination of somethings the mother and fetus are exposed to before the child is ever born. I could be wrong, but that is my guess. As for LarryG2, I do not for a moment believe that many cases of ASD are misdiagnosed behavior problems. I have spend too much time around ASD children the past few years to buy into that one.

    August 16, 2011 at 00:00 | Report abuse | Reply
  8. Laureth

    Often the ASD is misdiagnosed. My oldest daughter has Aspergers and was originally diagnosed with ADHD. We kept telling all the "professionals" that the diagnosis was wrong or at the very least, incomplete, but no one listened to us. What do we know anyway? We were just her parents and lived with her. We saw her behavior on a regular basis and knew there was more going on than the "professionals" believed. She didn't get the Aspersgers diagnosis until she was ten or eleven. She already had a little sister, but my younger daughter has no sign whatsoever of ASD. Having one child with ASD is a challenge, I can't imagine having two(or more).

    August 16, 2011 at 07:20 | Report abuse | Reply
  9. Melissa

    Of course there's a higher risk for the next siblings. Because most of the kids diagnosed with it aren't actually autistic. They are behaving badly which the parents then use autism as an excuse for their bad behavior and the parents inability to deal with it. In the 80's and 90's it was called ADHD or ADD. The younger siblings see this behavior and mimic it because they see that sibling getting away with murder, and it eventually becomes just the way things are. Here's an idea, parents how about you actually be a parent and sick it up.

    August 16, 2011 at 09:14 | Report abuse | Reply
    • Autism Mom

      Oh yeah, like an autism diagnosis is so much easier than disciplining a child? What planet are you on? Having a child in special edu, with all the sigma that still carries, doctor's appts, therapies, medications, head banging tantrums, trust funds and OCD. What great fun. And the heartbreak of having a frustrated, screaming child that can't communicate with you. An autism diagnosis is so much more serious than ADD/ADHD. You sound like the people that told me "oh, there's nothing wrong with him" (when he was 5 years old and couldn't talk to me), but I'm guessing you're really more like the co-workers that told me to "whip his little a$$" and make him behave.

      August 16, 2011 at 10:02 | Report abuse |
    • Stacey

      Wow, Melissa. It's obvious that you have no idea what you are talking about. I think we should blame bad parenting for everything. Your child has Down's Syndrome? It's because you're a bad parent. Cystic Fibrosis? Bad parenting, again. Same for getting the flu or a cold or whatever. That makes complete sense, doesn't it? No, the reason that there is a higher risk for later children in the same family is because there is a genetic component. My oldest son is high functioning autistic. He is five years older than his younger brother, who showed autistic behavior from the time he was very young. There was no way he was imitating his older brother, since 1) with that age gap, the behaviors that his older brother manifested at the same age were never witnessed by the younger one, and 2) some of the behaviors were different (ex, older brother was a "head banger" and younger brother was a "flapper" but both of those are autistic "stereotypic motor movements").

      August 16, 2011 at 10:54 | Report abuse |
  10. Elwyn

    This is NOT new information! Seven years ago I was doing research on identical twins and triplets, some with autism / some without, and their siblings. I was able to tell from a small blood sample which of the kids was autistic and predict which of their siblings would become autistic. This could have turned into a simple diagnostic test, but the head of my lab would not let us develop the test for clinical use and publish the results. As a side note, there was no link between vaccination and developing autism.

    August 16, 2011 at 10:20 | Report abuse | Reply
  11. William

    "This does not mean that every family who has a child with ASD will have a second child with ASD. It's just their risks are higher," noted Ozonoff."

    Makes sense...but remenber that birth control and other meds exists in our water supplies...Roundup and glycophospates saturate our foods, and genetically modified wheat/corn is everywhere. Until these are 100% ruled out be careful not to let a 'possible' genetic link become a smokescreen.

    August 16, 2011 at 11:19 | Report abuse | Reply
  12. Jan

    The study did not differentiate between the influence of shared genes or shared environment...Why can't we get information about environmental causes and insults that cause autistic behaviors in children and adults?

    "Dr. Joachim Hallmayer, a psychiatrist at the Stanford University School of Medicine, and his team report online in the Archives of General Psychiatry that shared environmental influences may account for as much as 55% of autism risk, while less than 40% can be attributed to genes."

    Read more: http://healthland.time.com/2011/07/05/study-environmental-factors-may-be-just-as-important-as-genes-in-autism/#ixzz1VDA0uucG

    August 16, 2011 at 12:51 | Report abuse | Reply
  13. Geralyn

    Your articles are for when it absolutely, positively, needs to be understood oervnihgt.

    October 9, 2011 at 17:09 | Report abuse | Reply
  14. bkbblzm

    nrXm3y sctejtqwogwj

    October 12, 2011 at 06:16 | Report abuse | Reply
  15. Roger Sleeter

    You have made some good points there. I checked on the web to find out more about the issue and found most people will go along with your views on this site.


    March 30, 2021 at 11:10 | Report abuse | Reply
  16. Paulita Gaede

    Pretty! This was an extremely wonderful article. Thank you for supplying these details.


    April 2, 2021 at 02:21 | Report abuse | Reply
  17. what is tadalafil

    generic tadalafil https://elitadalafill.com/ tadalafil dosage

    April 4, 2021 at 20:58 | Report abuse | Reply
  18. what is alprostadil

    injectable drugs for erectile dysfunction https://alprostadildrugs.com/ alprostadil penile suppository

    April 5, 2021 at 07:53 | Report abuse | Reply
  19. how does vardenafil work

    vardenafil vs viagra https://vegavardenafil.com/ how does vardenafil work

    April 5, 2021 at 21:23 | Report abuse | Reply
  20. Elite Proxies

    Oh my goodness! a tremendous article dude. Thank you Nonetheless I'm experiencing challenge with ur rss . Don’t know why Unable to subscribe to it. Is there anyone getting identical rss problem? Anyone who is aware of kindly respond. Thnkx


    April 8, 2021 at 02:58 | Report abuse | Reply
  21. Waylon Zecchini

    Hey very nice blog!! Man .. Beautiful .. Amazing .. I'll bookmark your blog and take the feeds also…I am happy to find a lot of useful information here in the post, we need develop more strategies in this regard, thanks for sharing. . . . . .


    April 14, 2021 at 14:43 | Report abuse | Reply
1 2

Post a comment


CNN welcomes a lively and courteous discussion as long as you follow the Rules of Conduct set forth in our Terms of Service. Comments are not pre-screened before they post. You agree that anything you post may be used, along with your name and profile picture, in accordance with our Privacy Policy and the license you have granted pursuant to our Terms of Service.

About this blog

Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.