The Rising Rates of Autism in the Age of Modern Medicine

Posted in Autism on 30. Nov, 2009

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Most people who are not on a mission to prove inoculations are the sole cause of autism would very easily concede that a large portion of the increased diagnostic rates of Autism Spectrum Conditions is due to increased recognition of the conditions, a broadening of the basic definition of “autism”, and better public awareness. Prior to the 1990s, autism was not considered a spectrum nor were Asperger’s Syndrome or PDD-NOS included in this now ever-broadening category. And even further back than that, Autistic Disorder itself was considerably more narrow, targeting mostly the moderate-functioning individuals while those on the lower end fell under the broad roof of Mental Retardation.

I, however, am not one to believe that autism is solely an issue of genetics and that rising rates are all just an illusion. Monozygotic (identical) twin studies very readily suggest the same and that while those studies confirm the extreme heritability of the conditions, they also stress that environmental factors are at play. What this multitude of factors are, since it’s undoubtedly not just one, will hopefully come to light with time.

But for all the factors suggested to have potential roles in the rising rates of autism diagnosis, there’s few to suggest that autism rates have risen simply because there are more autistic people.—There’s a fine line of distinction between saying a) there are more environmental factors in modern day human society which increase the risk of autism, and saying b) there are simply more autistic people being born. The latter has a greater genetic implication.

A number of epidemiological studies over the last decade or more have researched the rates of obstetric complications in relation to autism (Bolton et al., 1997; Kolevzon et al., 2007; Glasson et al., 2004). Many studies have repeatedly confirmed an increased risk of autism correlated with certain types of pre- and perinatal complications, such as low birth weight, differences in gestational duration, intrapartum hypoxia, increased infant distress, and so on. Most studies initially proposed that birth complications could cause autism, and while it’s undeniable that something like brain damage due to hypoxia (oxygen deprivation) isn’t going to help an autistic child succeed in life, more recent studies have instead opted to call these complications related “epiphenomena” (i.e., they don’t know why they’re associated with autism, they just are).

Few have gone on to consider what this implies. Even as recently as the early part of the 20th century, infant mortality rates were as high as 13.5% (Brosco, 1999) and even higher in centuries past. The infant mortality rate for 2008, according to the CDC, was approximately 0.7%. That means that between 1911 and 2008, a little over 100 years, the infant mortality rate has declined by about 19-fold. Many more people are living—people whose survival evolution would have otherwise selected against.

If families of autistics are more prone towards birth complications, then these birth complications would have meant that, prior to the age of medical intervention, many of these autistic children would not have survived long enough to have been diagnosed with autism, if the concept had existed at the time. Additionally, labor was a dangerous act for the mother, and maternal mortality has also decreased. Therefore, mothers of autistics, rather than dying in labor, can go on to have more children, possibly leading to more multiple incidence families.

It doesn’t take a rocket scientist to figure out that if more autistic people are surviving beyond the perinatal period, then the rates of diagnosis will also increase. Also, if these autistic children grow up and have autistic kids of their own (an effect that would take more than a single generation to be realized), then occurrence rates could increase exponentially.

Taking the intervention of modern medicine into consideration, it’s plausible that increased infant survival rates, the high genetic heritability of the conditions, and additional environmental factors may have all made the 20th century an incubation period for autism, which is only now catching up to public awareness.

References:

Bolton, P.F., Murphy, M., MacDonald, H., Whitlock, B., Pickles, A., & Rutter, M. (1997). Obstetric complications in autism: Consequences or causes of the condition? Journal of the American Academy of Child and Adolescent Psychiatry, 36(2), 272-281.

Brosco, J. P. (1999). The early history of the infant mortality rate in America: “A Relfection upon the Past of Prophecy of the Future”. Pediatrics, 103(2), 478-485.

CDC. (2008). CDC releases new infant mortality data. Centers for Disease Control and Prevention. Retrieved on 11/15/2009 from: http://www.cdc.gov/media/pressrel/2008/r081015.htm?s_cid=mediarel_r081015

Glasson, E. J., Bower, C., Petterson, B., de Klerk, N., Chaney, G., & Hallmayer, J. F. (2004). Perinatal factors and the development of autism. Archives of General Psychiatry, 61, 618-627.

Kolevzon, A., Gross, R., & Reichenberg, A. (2007). Prenatal and perinatal risk factors for autism: A review and integration of findings. Archives of Pediatrics and Adolescent Medicine, 161(4), 326-333.

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