Study says environment plays role in Autism: nongenetic factors include parental age,low birth weight

Nongenetic risk factors that may index environmental influences include parental age,low birth weight, multiple births, and maternal infections says this study from the July 2011 of the Archives of General Psychiatry.

Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism

ABSTRACT

Context Autism is considered the most heritable of neurodevelopmental disorders, mainly because of the large difference in concordance rates between monozygotic and dizygotic twins.

Objective To provide rigorous quantitative estimates of genetic heritability of autism and the effects of shared environment.

Design, Setting, and Participants Twin pairs with at least 1 twin with an autism spectrum disorder (ASD) born between 1987 and 2004 were identified through the California Department of Developmental Services.

"The finding of significant influence of the shared environment, experiences that are common to both twin individuals, may be important for future research paradigms. Increasingly, evidence is accumulating that overt symptoms of autism emerge around the end of the first year of life. Because the prenatal environment and early postnatal environment are shared between twin individuals, we hypothesize that at least some of the environmental factors impacting susceptibility to autism exert their effect during this critical period of life. Nongenetic risk factors that may index environmental influences include parental age, low birth weight, multiple births, and maternal infections during pregnancy. Future studies that seek to elucidate such factors and their role in enhancing or suppressing genetic susceptibility are likely to enhance our understanding of autism."
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Also in this issue of Archives of General Psychiatry Antidepressant Use During Pregnancy and Childhood Autism Spectrum Disorders