Multiple lines of converging evidence document brain enlargement in autism. Magnetic resonance imaging (MRI) studies have revealed generalized enlargement in the cerebral cortex and some subcortical structures by the age of 2 years. Studies of head circumference among high-risk infants suggest that brain overgrowth begins at 6-12 months, and behavioral studies of infants suggest that the defining features of autism generally appear by 12 months of age.

The study of autism is best approached using a variety of disciplines, a practice greatly facilitated by the large amount of data shared among collaborators in the Simons Simplex Collection. Steve Petersen and his colleagues at Washington University in St. Louis plan to contribute new brain imaging data to the mix using a recently developed tool called resting-state functional connectivity MRI (fcMRI).

The heritable nature of autism has been borne out by research showing that identical twins and siblings of children with autism are at a greater risk of the disorder than children in the general population. Zachary Warren and his colleagues at the Vanderbilt Kennedy Center plan to follow 66 such school-aged siblings to gauge cognitive, language and behavioral outcomes.

22q11 deletion syndrome is among a growing number of genomic disorders that are associated with autism, and is one of the most common recurrent copy number variants (CNVs) — deletions or duplications of DNA — associated with altered development of social-communication, language and behavioral skills.