A just-released study of twins by researchers at UCSF and Stanford suggests that environmental conditions may be at least as relevant as genes in causing autism. We speak with the lead authors about how these findings may challenge conventional wisdom about the origins of autism.

Joachim Hallmayer, associate professor of psychiatry and behavioral sciences at Stanford University and lead author on the autism paper
Neil Risch, director of the Institute for Human Genetics and professor of epidemiology and biostatistics at the UCSF Institute for Human Genetics and senior author of the autism study
Daniel Coury, chief of developmental and behavioral pediatrics at Nationwide Children's Hospital in Ohio and medical director of the Autism Treatment Network for Autism Speaks, an autism science and advocacy organization which was involved in funding the new research

  • Glenn in Berkeley

    Michael, please ask your guests to comment on the vitamin D hypothesis, in particular the coincidence if the autism epidemic with the widespread use of highly effective sunscreens and the very widespread low vitamin d levels in women and pregnant women.

    Did they interview the parents with respect to sunscreen use? Was there a north south gradient in their data.

    • Alice

      And vitamin D deficiency is a causal factor in depression,

      • Friendly Snake

        Please do a quick literature review on the current research on Vitamin D’s role in development and any other pertinent research. If the arrows point the right way, I bet someone would fund the grant.

  • landonbryce

    I am concerned to which we focus on factors such as chemicals when we think of environmental triggers for autism.  Have the researchers ever considered issued such as noise and sound pollution, which may also affect neural development?

  • Alyssa

    Hello, I am a mom of 2 kids ( a boy and a girl, not twins) who both have Autism.  I did everything seemingly “right” during both pregnancies: took my supplements, no drugs, a healthy diet, exercise.  Both of my children were born in Los Angeles and I’ve often wondered if we’d lived in a different area of the country would they still have Autism, and if there was something in our home environment that could have affected them.  BTW, both my husband and I have cousins, a few times removed, who have Autism, as well.

  • Daisy

    I do ABA therapy (applied behavioral analysis) with children with Autism and I’ve heard a lot about different kinds of treatments.  I’m wondering what these findings mean for the efficacy of the different treatments.

  • Libby

    In the light of this study being about multiple births I’m wondering if the increased use fertility drugs might be a factor.

    • Cemekeller

      Great question. I’d love to know, too!

  • laurie

    Have your researchers looked at the high rate of autism in Somali children in Minneapolis

  • Les Albiol

    Has there been any investigation in regards to epigenetics (changes produced in gene expression caused by mechanisms other than changes in the underlying DNA sequence) and a possible relationship to Autism (or other conditions that seem to be inexplicably on the increase)? Perhaps environmental conditions that parents or grandparents were exposed to are now manifesting in this generation?

  • Bob

    Is there a possibility that autism could also be caused by brain damage due to mis-use of forceps during birth delivery? It seems to have been shown that this could be one cause of cerebral palsy and other developmental disabilities. Can autism be mis-diagnosed as cerebral palsey, or vice-versa?

  • Glenn in Berkeley

    Michael, you’ve given your guests two cuts at the vitamin D question, but clearly the don’t want to comment. Please get them on record.

  • Criss Deguzman

    I am the mom of fraternal twins one of which is severely autistic and had the twins when I was 37 years old.  I did not take SSRIs, took my prenatal vitamins and lived in a non-polluted area  during the twins’ conception and early childhood. What does your research mean in terms of finding a cure or preventive measures for prospective parents?

  • Donna Harrison

    Are you finding toxic indicators in blood tests in your study?

  • ruzica63

    Question is for Dr Risch

  • ruzica63

    Question is for Dr Risch: What percentage of the children on the spectrum show higher than typical incidence of auto-immune system dysfunction and high oxidative stress?  Also a presence of  severe gut dysbiosis and how it can possibly affect their behaviours?   

  • Muuaaa

    It’s Vitamin D3 deficiency that causes Autism.

  • Joanne B Ruby

    Findings of the twin study discussed today suggest that
    environmental factors are related to the development of autism spectrum
    disorders.  The findings of the other
    study released in the same journal showing an association between mothers’ use
    of antidepressants during pregnancy and a child’s risk for autism also support
    the need to for more research on environmental factors — specifically events
    during pregnancy.


    It is important that listeners know that the examination of
    possible environmental risk factors for developing autism spectrum disorders is,
    in fact, the focus of two national studies currently underway – both the
    largest of their kind, both happening at Kaiser Permanente Division of


    EARLI, the Early Autism Risk Longitudinal Investigation, is
    a study taking place in four National Institute of Health-funded sites, following
    1200 mothers of children with autism at the start of another pregnancy and
    documenting the newborn child’s development through age 3.  (www.earlistudy.org).


    SEED, Study to Explore Early Development, is the largest
    national autism study to date, funded by the CDC, that is looking at possible causes
    and risks for developmental delays and ASDs by enrolling children ages 2 to 5 (www.cdc.gov/seed).


    English and Spanish speaking families are needed for both studies.  To find out more, please contact us at the
    Autism Research Program at Kaiser Permanente Division of Research (www.autismresearch.kaiser.org).  We truly need to work together to move the
    science forward. 

    Joanne Ruby
    Outreach Coordinator
    Autism Research Program
    Kaiser Permanente Division of Research

  • Celine

    By defining  environmental factors as primarily what happens in the mother’s womb, don’t we risk creating another version of blaming the mother for autism–not as refrigerator mothers but as poisonous mothers.

    • Friendly Snake

      Human reproduction obviously causes Autism. Is there anything we can do to insulate our race from this horrible truth? 

      In all seriousness though, you have a valid point. It’s a fine line to walk. However, I believe that the antidote is not to fear the possibilities that we’ll blame mothers, but to clearly understand that mothers are literally the source of all human life and thus will most likely by at least tangentially involved in any difficulties that arise in bringing that life into the world. Just my 2 bucks.

  • Autismdr

    Those of us who treat these kids every day recognize the multitude of biochemical and neurological issuses these kids deal with.  Unfortunately, most doctors never look beyong the diagnosis and all other physiological issues are due to the ‘Autism”.  Crazy.

    Dr. Mike

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