Developmental Trajectories in Children With and Without Autism Spectrum Disorders: The First 3 Years


  • We thank the participants and staff at Kennedy Krieger Institute and The Lurie Center, LADDERS of Massachusetts General Hospital for their help in data acquisition, coding, and/or processing. Special appreciation is expressed to Dr. Margaret Bauman for her oversight of the data collection at the Lurie Center-MGH, Massachusetts General Hospital, Harvard Medical School. All authors had full access to all of the data in the study; Dr. Landa and Ms. Faherty take responsibility for the integrity of the data; Dr. Gross and Dr. Stuart take responsibility for the accuracy of data analysis. We extend our gratitude to Drs. Mary Blue, Carlos Pardo, and Michael V. Johnston for their comments on the neurobiological theories of ASD we discussed herein. The authors have no conflicts of interest to report. Funding from the National Institute of Mental Health, awarded to Rebecca Landa (PI): MH59630 (design, study conduct, data collection, management, analysis, interpretation; preparation, review, and approval of manuscript), Autism Speaks (data collection), and U54 MH066417-04 (data collection).

Correspondence concerning this article should be addressed to Rebecca J. Landa, Kennedy Krieger Institute, 3901 Greenspring Avenue, Baltimore, MD 21211. Electronic mail may be sent to


Retrospective studies indicate 2 major classes of autism spectrum disorder (ASD) onset: early and later, after a period of relatively healthy development. This prospective, longitudinal study examined social, language, and motor trajectories in 235 children with and without a sibling with autism, ages 6–36 months. Children were grouped as: ASD identified by 14 months, ASD identified after 14 months, and no ASD. Despite groups' initial similar developmental level at 6 months, ASD groups exhibited atypical trajectories thereafter. Impairment from 14 to 24 months was greater in the Early-ASD than the Later-ASD group, but comparable at 36 months. Developmental plateau and regression occurred in some children with ASD, regardless of timing of ASD diagnosis. Findings indicate a preclinical phase of varying duration for ASD.