Autism, Genetics, and Family: New Questions
To say that “autism is genetic” is not to say that there is some “autism gene” that can be clearly singled out. An article on Williams Syndrome in the July 8th New York Times magazine highlights the interplay between genes and “environment.” Those with Williams have “mild to moderate mental retardation or learning difficulties, a distinctive facial appearance, and a unique personality that combines overfriendliness and high levels of empathy with anxiety”; Williams occurs because of a “small genetic accident” or genetic mutation, in which a small section of chromosome 7 that contains approximately 25 genes is deleted. Writes David Dobbs in The Gregarious Brain
…..genes (or their absence) do not hard-wire people for certain behaviors. There is no gene for understanding calculus. But genes do shape behavior and personality, and they do so by creating brain structures and functions that favor certain abilities and appetites more than others. [my emphasis]
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M.I.T. math majors aren’t born doing calculus, and people with Williams don’t enter life telling stories. As [Stanford University Medical Center psychiatry professor] Allan Reiss put it: “It’s not just ‘genes make brain make behavior.’ You have environment and experience too.”By environment, Reiss means less the atmosphere of a home or a school than the endless string of challenges and opportunities that life presents any person starting at birth. In Williams, he says, these are faced by someone who struggles to understand space and abstraction but readily finds reward listening to speech and looking at faces. As the infant and toddler seeks and prolongs the more rewarding experiences, already-strong neural circuits get stronger while those in weaker areas may atrophy. Patterns of learning and behavior follow accordingly.
To speak of genes “versus” the environment is a “false dichotomy.” The “vaccine court” hearings and recent attention given to the MMR vaccine and Andrew Wakefield attest to a continued search—-a “hunger“—-to find some single cause of autism; as Reiss points out, genes, environment, and experience all play a role. John Timmer in the July 8th Ars Technica describes an Open Access study that shows “extensive genetic overlap” among complex human phenotypes, and with autism and a number of other diseases:
To get some statistical power behind the analysis of this question, the researchers involved turned to a massive database containing over 1.5 million patient records from Columbia University Medical Center. The authors checked for both positive and negative correlations among a collection of 161 disorders, ranging from infectious diseases through mental illnesses. They controlled for age of onset, made a few basic assumptions (which are detailed in the paper), and then crunched all the combinations, looking for positive and negative correlations between pairs of diagnoses.
Some of the results acted as positive controls for the technique. For example, Fragile X syndrome can be diagnosed in part via autism as a symptom, and a link between the two did come out of the study. But autism wound up linked to a huge variety of neural diseases with symptoms that appear far later in life, such as attention deficit, epilepsy, cerebral palsy, depression, schizophrenia, bipolar disorder, neurofibromatosis, Parkinson’s disease, and migraine. [my emphasis] But those extensive linkages don’t mean that all mental disorders form a single large cluster; neurofibromatosis showed a correlation with bipolar disorder, but not schizophrenia, even though all are linked to autism.
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Based on the strengths of various connections, the authors suggest they can calculate the degree to which similarities are shared on the genetic level. For example, they estimate that somewhere between 20-60 percent of the variations that predispose someone to autism also predispose them to bipolar disorder. Similar figures were found for an autism-schizophrenia link.
This study can be said to open more questions, rather than to provide answers: What does it mean that “20-60 percent of the variations that predispose someone to autism” also predispose them to bipolar disorder, or to schizophrenia? If some interplay between genes and the environment might lead to autism, is it really possible to develop something like a blood test or other prenatal test?
And, as we learn more about the genetics of autism, new questions arise, such as whether families should own genetic information?, as Hsien Hsien Lei asks Eye on DNA. What will be the impact of knowledge about autism and genetics not only on our understanding of autistic persons, but on families in which there is an autistic relative?
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POSTED IN: Cause, Environment, Family, Genetics, Health, Psychiatry, Science
5 opinions for Autism, Genetics, and Family: New Questions
resilientmom
Jul 9, 2007 at 9:59 am
This website is comprehensive and valuable.
My circumstance adds credence to a myriad of suggestions in this artice.
Our child affected with autism is one in a set of quadruplets. He is the only one of his siblings that is on the spectrum. He did have a medical insult at 6 months of age, where he had a cardiac arrest due to a lung cyst, which was subsequently removed.
Naturally, following anoxia, we looked for symptoms accompanied with oxygen deprivation. The only obvious issue was that he “seemed deaf”.
That started our journey to the diagnosis of autism, which many parents ultimately experience (the hearing question).
The environmental stimulus in our home, was that of 3 other children who beckoned his attention. Admittedly, the first 5 years were eventless, in that it did not matter to him that they existed. Eventually, their presence became of paramount importance, and he responded to their being part of his world.
Specialists credit our son’s zealous interest in people, to the fact that he was raised in a family of 6, and was never allowed to retreat, due to the sheer numbers in his household.
Genetics? Environment? The questions remain.
Respectfully,
Resilientmom
http://www.revolutionhealth.com/blogs/resilientmom
Kristina Chew, PhD
Jul 9, 2007 at 1:19 pm
Sounds like a fabulous household for him to be in—-my son is an only child. We have been living with my husband’s elderly parents and a live-in nurse for the past year and it has been a very good thing for him to live with other people and learn to be in a household that is not always focused on him. Best wishes—-
M'sDad
Jul 9, 2007 at 1:40 pm
Kristina - once again a phenomenally useful and helpful post, aiming for a balanced understanding of the complexity of autism - thanks! I feel somewhat peevish for picking a nit, however; you observe that the controversy over the “vaccine court” and Wakefield has fed discussion of a “single cause” theory, but it’s not clear to me that Wakefield subscribes to the idea that the MMR is a “single cause”; whether or not one believes that his work is “junk science” and/or that he is a borderline malicious opportunist, my understanding is that his contention has been that the MMR is a trigger for GI disturbances in some children because of their specific genetic makeup… and those GI disturbances create neurological disruption as well.
Certainly at least one of the doctors associated with the clinic Wakefield co-founded (Thoughtful House, in Austin TX) seems to be taking a “genetic predisposition, variety of possible harmful environmental triggers” tack with his recent book, Changing the Course of Autism. Granted, he still medicalizes the definition and approach to autism, but after all, that’s his professional background…
Of course, in our litigious society, if there is a court set up for litigation over a particular type of “trigger” (especially if the litigation is against a category of company that is easily characterized as “big and nasty and profiteering”), it makes perfect sense that parents in search of financial resources would (attempt to) emphasize that trigger. Much harder to go after more diffuse environmental triggers, let alone internal biological/developmental triggers.
The more I read and think, the less convinced I am by the vaccine theory; and I don’t think I buy the MMR theory either (especially for the overwhelming majority of the population; I’m less certain that there are absolutely *no* children whose genetic makeup is such that they *would* indeed be harmed by a live-virus measles vaccine, but proving a negative is notoriously impossible). But I also think that partisans on both sides have found it useful to demonize the opposite side by characterizing its positions as stark and non-nuanced, and I’m not sure that is all that helpful in moving toward a better set of resources (however one chooses to define that) for individuals with autism… another reason why I am so grateful for the low-partisanship buzz of this blog. Thanks again, Kristina!
Kristina Chew, PhD
Jul 9, 2007 at 8:59 pm
And I hope to keep it that way……… I was using the notion of a “single cause” in a more general sense, as you note, in reference to theories of autism causation that “single out” one thing in particular (the MMR vaccine; one could say that Bettelheim’s theory was also a “single cause theory,” with the cause being parents). Single cause theories need particularly to be treated with care due to their seeming to provide single courses of treatment….
What Do You Think About Genetic Testing and Autism?
Jul 12, 2007 at 7:14 pm
[…] is currently no genetic test for autism; the mention of one can incite a serious discussion: If there were a prenatal genetic test for autism, and if expecting parents found out that they […]
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