Genetic and neurodevelopmental influences in autistic disorder.
OBJECTIVE
In the past, autism was considered to be largely psychogenic. However, research in the last 2 decades indicates that autism is largely caused by genetic factors that lead to abnormal brain development. This article reviews research into the genetic and neurodevelopmental factors underlying autism.


METHODS
We review the findings from genetic and brain-imaging studies of autism over the past 15 years and synthesize these findings as a guide for future research.


RESULTS
Genome scans and association studies have suggested potential genomic regions and genes, respectively, that may be involved in the etiology of autism, and there have been some replications of these results. Similarly, the findings that brain volume is exaggerated in autism and corpus callosum size is reduced have also been independently replicated. Unfortunately, studies of other subcortical structures remain inconclusive or contradictory.


CONCLUSIONS
Overwhelming evidence now supports a neurobiological basis for autism. However, further refinements will be needed to guide future studies, particularly to identify the most informative phenotypes to investigate. Additionally, studies examining the role of genetic factors in the brain abnormalities underlying autism will likely lead to further findings that will enhance our understanding of autism's causes.
Department of Psychiatry, University of Western Ontario, London, Ontario. Rnicolso@uwo.ca
Rob
R
Nicolson
Peter
P
Szatmari
D061085:Agenesis of Corpus Callosum; D001321:Autistic Disorder / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology*; D001921:Brain / Q000002:abnormalities / Q000378:metabolism / Q000503:physiopathology*; D002531:Cerebellum / Q000002:abnormalities / Q000378:metabolism; D002648:Child; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D006801:Humans; D008279:Magnetic Resonance Imaging; D010641:Phenotype; D012701:Serotonin / Q000378:metabolism; D013702:Temporal Lobe / Q000002:abnormalities / Q000378:metabolism
D012701:Serotonin