To understand the mechanisms behind autism, researchers grew miniature human brains from the stem cells of autism patients. The resulting "brain organoids" revealed that a genetic mutation causes the brain to overproduce inhibitory neurons, which dampens how signals are transmitted within the brain, according to research published today in Cell.

Despite advances in the past few years, researchers still don't know what causes Autism Spectrum Disorder (ASD). They're pretty sure that genetic and environmental factors come together to create the neurological conditions that result in impaired social interaction. Past studies have focused on the genetic mutations found in those with ASD. While that has revealed a handful of mutations that may cause the disorder, that only accounts for one to two percent of autism patients. Researchers had been using the genetics to arrive at the biology, and it was proving to be pretty challenging.