A total of 102 families living in 22 states throughout the U.S. successfully completed the study with data recorded from 102 children with autism and 98 siblings.

All participating families were recruited from Simons Powering Autism Research (SPARK). SPARK families were contacted by email with the opportunity to join the SSP if they had two adolescent children who were full siblings, 10-17 years old, one with a parent-reported medical diagnosis of autism and the other without.

All children had completed whole-exome sequencing, which did not yield any returnable autism-related genetic results (all participants with autism had idiopathic autism), and all children with autism exceeded the autism cutoff score (>15) on the Social Communication Questionnaire, Lifetime Edition, which was completed by a caregiver at the time they joined SPARK.