Autism is a general term for a spectrum of disorders of brain development that range in severity from mild to severe. Because autism is not a single disease, it has been difficult to identify its causes. Dr. Christopher Walsh describes how recent advances in DNA sequencing technology have made it possible to study large cohorts of patients and find genes that are most commonly disrupted in children with autism. These studies show that all currently known genes associated with autism are also associated with other neurological diseases, and that they affect the mechanisms of communication between neurons.