Genes are bigger contributors to autism features than are environmental factors, according to a study of nearly 39,000 twins1.
Autism traits such as repetitive behaviors or resistance to change are about 80 percent heritable, the study found. Previous twin studies estimated that genes account for up to 95 percent of autism risk.
“This study tends to confirm that development of autistic traits is indeed due to heritability, and not so much due to whatever parents do or don’t do,” says lead researcher Dorret Boomsma, professor of biological psychology at Vrije Universiteit in Amsterdam in the Netherlands.
The researchers also mined the data for potential sex differences in the genetics of autism.
Looking at data from 6,400 boy-girl twins, Boomsma and her colleagues used statistical techniques to tease out whether different genes contribute to autism in boys than in girls. If different genes are at play, scores between boy-girl twins should vary to a different degree than do scores of same-sex fraternal twins.
The analysis showed no such systematic difference in scores. This result suggests that the same genes influence autism traits in boys and girls.