Epigenetic Causes

Page by Stephanie Watkins

Differences in response to treatment, family history, longitudinal outcomes, and clinical features have led researchers to believe that the development of autism is one resting on both genetic and environmental principles (Fombonne, 2003). Building off psychology’s antecedent in philosophy, the debate between nature versus nurture continues to exist today in terms of our struggle to find a cause of autism spectrum disorders.  Nurturists, such as John Locke, thought of individuals as a blank slate, drawing all influence and growth from individual circumstances. On the other hand, nativists, such as Rene Descartes, urged that individuals were born with a genetic predisposition from which all development was based (Thorne & Henley, 2005). Although this argument came into existence hundreds of years ago, its main themes and components are evident in the research determining the etiology of autism.

Although many parents continue to believe that a single cause for their child’s autism exists, this is generally agreed to be a misconception. Basing off the psychanalytic, neurodevelopmental, and alternative theories of causes of autism spectrum disorder, there are an infinite number of ideas applying to some individuals and not others. Furthering this idea, while many theories have been proven to be false, a stigma continues to exist.Recent technological advances in neuroimaging techniques, as well as genetic mapping, have allowed researchers to gain a more empirical understanding of the causes of autism. Despite modern advantages, twin studies demonstrate that nonoverlapping genes act on many traits, failing any attempt at a single explanation for the development of autism. Because of discrepancies in the literature, some theories being supported and others refuted, one issue has been that researchers have been searching for causes of autism as a whole, disregarding its behavioral, cognitive, and genetic levels. Although many children fit the diagnostic criteria for autism, many show isolated difficulties in only one area of the autistic triad, representing the classification as a spectrum disorder (Happe, Ronald, & Plomin, 2006). In twin studies, genes are expected to account for approximately 50% of the variation between twins, but what accounts for the remaining percentage?No single deficit has been identified as the cause for the full triad of social, communicative,  and repetitive difficulties (Happe et al., 2006). It is suggested, by some, that it is time to give up on the search for a single explanation for autism and molecular genetic studies should instead search for linkage to each of autism’s respective 3 components.

This is where the alternative and environmental causes of autism spectrum disorder come into play. Perhaps solely acting on a genetic predisposition for autism, particular environmental surroundings are necessary for the disorder’s expression. The sudden increase in incidence of autism suggests the contribution of environmental factors and genetic risk, only developing in cases in which both components are evident. In examining particular components of the environment, such as diet or poor parenting, many have been proven false when taken into consideration alone. A redox/methylation hypothesis has been suggested, relying on the idea that individuals are genetically sensitive and certain environmental factors act on such susceptibility (Deth, Muratore, Benzecry, Power-Charnitsky, & Waly, 2008). Both genetic and environmental factors play important roles in defining the risk of autism, reflecting the idea of epigenetic causality.

References:

Fombonne, E. (2003). Modern views of autism. The Canadian Journal of Psychiatry, 48(8), 503-505.

Happe, F., Ronald, A., & Plomin, R. (2006). Time to give up on a single explanation for autism. Nature Neuroscience, 9(10),  1218-1220.

Thorne, M. B. & Henley, T.B. (2005). Connections in the history and systems of psychology (3rd ed.). Boston: Houghton Mifflin.

Images/Video:

World Autism Awareness Image: http://keithsouza.com/wp-content/uploads/2009/04/logo-waad.jpg

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