Parental age at child's birth--which has steadily increased in the U.S.--is strongly associated with heightened risk of autism. By analyzing patterns of concordance for autism among twin pairs, we identify a central mechanism for this association: de novo mutations, which are deletions, insertions, and duplications of DNA in the germ cells that are not present in the parents' DNA sequence. We show how a social demographic change like rising parental age can yield genetic changes that, at the population level, combine to contribute to the increased prevalence of autism.
Read our paper: Liu, K., Zerubavel, N., & Bearman, P. (2010). Social Demographic Change and Autism. Demography, Volume 47, Issue 2:327-343