Autism: Is It Caused By A Toxic Womb?
Is the mother to blame redux?
Posted Jul 30, 2011
In graduate school, I had the interesting experience of working with Bruno Bettelheim at his then world-famous Orthogenic School. Bettelheim has received much posthumous bad press, some of it personal--allegations of physical abuse--and much of it professional--his idea that autism was caused by the environment, specifically, having what he called an emotionally cold "refrigerator mother."
Bettelheim's specific idea of toxic parenting as the cause of autism has been long discredited, and replaced with the idea that autism is genetic.
In 1977, a study, "Infantile autism: a genetic study of 21 twin pairs," by Folstein and Rutter (J Child Psychol Psychiatry. 1977; 18), found that among identical twins--those sharing 100 percent genes, had a concordance rate of 90 percent, while fraternal twins--those with only half their genetic makeup in common, who are no more alike than any other siblings of shared parents--had a concordance rate of zero.
These results puzzled many observers who had informally observed a concordance rate of approximately 10 percent for autism among non-twin siblings, writes Peter Szatmarti in a recent review in the Archives of General Psychiatry. Szatmarti adds that despite the presumed heritability of autism, there has been little insight into exactly what genetic components are responsible for the disorder.
A recent study has put more chinks into the armor of the heritability of autism, suggesting, says Szatmarti, that the "original estimates were inflated" for identical twin concordance, and underestimated for fraternal twins.
This new study, "Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism," by Joachim Hallmayer and colleagues (Arch Gen Psychiatry, 2011; 76) looked at 192 twin pairs in California in which at least one of the twins had autism.
Not to their surprise, they found that 77 percent of male twins, and 50 percent of female twins, shared an autism diagnosis.
Somewhat to their surprise, they found a fairly high number of fraternal twins who both had an autism diagnosis--31 percent for males, and 36 percent for females.
These findings point to some environmental factor associated with the development of autism.
They do not revive either Bettelheim's refrigerator mother, or provide support for environmental factors, such as toxic vaccines.
Rather, it seems to point to the womb itself--or other aspects of a shared gestation--as having an influence, particularly, when you compare the concordance rates for fraternal twins--above 30 percent--to that of non-twin siblings, somewhere between 10 and 20 percent.
There is still a strong genetic component to the development of autism, and it is probably what geneticists call polygenic. Simply put, with polygenic heritability, if you have 100 percent of the relevant genes, you will probably develop the disorder no matter how benign your environment. If you have none of the relevant genes, you will probably not develop the disorder no matter how toxic your environment. And if you have, say, 50 percent of the relevant genes, your environment--how benign or toxic--will matter a great deal in whether you become autistic.
Among the environmental factors at play may be the age of the mother, the age of the father, maternal genotype, some kind of immune reaction in the womb, in vitro fertilization, maternal drug use, maternal illness during the pregnancy such as diabetes or infections, or toxic elements in the environment. In other words, many of the usual suspects.
Ironically, these results may be confounded by the possibility that being a twin itself may somehow be a factor for autism. How else to explain the fact that concordance rates, in this new study, for fraternal twins are much higher than among other siblings?
But once again, we can go back to blaming the mother, although not at all in the way that Bettelheim or his psychodynamic fellow travelers may have intended.