Participants

This study was approved by the institutional review board at the University of Utah. Study participants were recruited from the community and received remuneration for their voluntary participation. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. All study participants provided written informed assent or consent prior to study participation with parental or legal guardian consent required of all study participants younger than 18 years. Participants included in this study were part of a larger and ongoing longitudinal study that began in 2003 aimed at investigating brain development across the adolescent and adult life span in individuals with autism. Methods used to acquire and analyze the resting-state fMRI data reported on in this study had not been used during any previous longitudinal study time points and incorporate data acquired between December 2016 and April 2018 and analyzed between January 2018 and April 2018. Autism diagnoses were established for each participant on initial inclusion into the longitudinal sample, based on the Autism Diagnostic Observation Schedule (ADOS)–Generic²⁰ (earlier entries) or the second edition of the ADOS-2²¹ (later entries), Autism Diagnostic Interview–Revised,²² the Diagnostic and Statistical Manual of Mental Disorders, fourth edition,²³ the Diagnostic and Statistical Manual of Mental Disorders, fifth edition,²⁴ and International Classification of Diseases, Tenth Revision criteria. For the current time point in the longitudinal sample, the ADOS-2 was administered to all individuals with autism spectrum disorder. Detailed demographics of participants are included in the Table.

Abbreviations: ADOS, Autism Diagnostic Observation Schedule; CSS, Calibrated Severity Score; FSIQ, full-scale IQ; NA, not available; PIQ, performance IQ; RRB, restricted and repetitive behaviors; SA, social affect; SCI, Social Communication Index; SRS, Social Responsiveness Scale; VIQ, verbal IQ.