Autism is a neurodevelopmental disorder generally detected around two to four years of age. Symptoms from the Wikipedia Autism Entry include abnormal social interaction, communication ability, patterns of interests, and patterns of behavior.

Interesting Research: As part of the Autism Genome project, researchers are trying to determine the genetic basis behind the heritable predisposition of Autism via Affymetrix 500K genotyping chips. For more information visit Press release.

Recent MRI research done on infants zero to two years of age showed that autistic infants have an abnormal increase in head circumference size (a predictor of brain size) relative to normal infants at around one year. By the end of the second year, an autistic infant has experienced much greater brain growth relative to normal. From two to four years, there is an increase in gray and white matter in the frontal and temporal lobes and the development of an abnormal ratio of gray to white matter in the cerebellum. Between five and twelve years of age, the autistic brain no longer shows a significant size difference from the normal (Hazlett).

References: Hazlett, HC (2005). “Magnetic resonance imaging and head circumference study of brain size in autism: birth through age 2 years.” Archives of General Psychiatry. Dec;62(12):1366-76.

Courchesne, E. (2004). “The autistic brain: birth through adulthood.” Current Opinions in Neurology. Aug;17(4):489-96.