A large study identifying common genetic variations that contribute to five different psychiatric disorders, including autism, sheds light on the disorder’s genetic architecture, says Benjamin Neale.

A comparison of autism-like behaviors in nearly 10,000 pairs of fraternal twins suggests that girls are somehow protected from the disorder. The findings, published 19 February in the Proceedings of the National Academy of Sciences, may partly explain why autism is four times more common in boys than girls.

Some Chinese individuals with autism have rare mutations that may disrupt the production of melatonin, the hormone that regulates sleep, according to a study published 17 January in PLoS One.

A group of genetic variants that are linked to schizophrenia do not seem to be associated with autism, according to a study published in the January issue of the American Journal of Medical Genetics Part B.

Members of families that have multiple children with autism have more features of the disorder than do those from families that have only one child with autism, according to a study published 2 November in the Journal of Autism and Developmental Disorders.

Solving the riddle of autism genetics will require looking beyond the growing list of candidate genes to epigenetics and personalized medicine.

A genetic panel intended to predict the risk of developing autism debuted for clinical use in April, while another is in commercial development and a third was published in Molecular Psychiatry in September. But some experts are concerned, saying the tests are based on preliminary scientific evidence.

Mutations in SHANK3, a leading autism risk gene, occur in roughly two percent of individuals with autism spectrum disorders, according to a study published 15 August in the European Journal of Human Genetics.

People with a certain variant in RBFOX1, a gene linked to autism risk, have a smaller temporal lobe than those with other variants, according to research presented Monday at the 2012 Society for Neuroscience annual meeting in New Orleans.

Individually, common genetic variants confer little risk for autism. But taken together, they may contribute significantly, predicts a statistical analysis published 15 October in Molecular Autism.