Objective-To examine prospectively the emergence of behavioral signs of autism in the first years of life in infants at low and high risk for autism.Method-A prospective longitudinal design was used to compare 25 infants later diagnosed with an autism spectrum disorder (ASD) with 25 gender-matched low-risk children later determined to have typical development. Participants were evaluated at 6, 12, 18, 24, and 36 months of age.Correspondence to: Dr. Ozonoff, M.I.N.D. Institute, University of California Davis Health System, 2825 50 th Street, Sacramento CA 95817; sally.ozonoff@ucdmc.ucdavis.edu. Disclosure: Drs. Ozonoff, Iosif, Cook, Hutman, Rogers, Rozga, Sigman, Steinfeld, and Young, and Mr. Baguio, Ms. Hill, and Ms. Sangha report no biomedical financial interests or potential conflicts of interest.Editorial support for the preparation of this article was provided by Diane Larzelere, UC Davis. NIH Public AccessAuthor Manuscript J Am Acad Child Adolesc Psychiatry. Author manuscript; available in PMC 2010 August 17. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptFrequencies of gaze to faces, social smiles, and directed vocalizations were coded from video and rated by examiners.Results-The frequency of gaze to faces, shared smiles, and vocalizations to others were highly comparable between groups at 6 months of age, but significantly declining trajectories over time were apparent in the group later diagnosed with ASD. Group differences were significant by 12 months of age on most variables. Although repeated evaluation documented loss of skills in most infants with ASD, most parents did not report a regression in their child's development.Conclusions-These results suggest that behavioral signs of autism are not present at birth, as once suggested by Kanner, but emerge over time through a process of diminishment of key social communication behaviors. More children may present with a regressive course than previously thought, but parent report methods do not capture this phenomenon well. Implications for onset classification systems and clinical screening are also discussed. KeywordsAutism; Onset; Infancy; Regression This study examined when and how behavioral signs of autism spectrum disorders (ASD) emerge in the first years of life. Most previous investigations of this topic have been retrospective, relying on parent report of earlier development or analysis of home videotape of infants later diagnosed with ASD. The existing literature suggests that behavioral signs of autism emerge in two different patterns, an early onset and a regressive course.Retrospective studies have demonstrated that children with early-onset ASD differ from agematched children with delayed and typical development in orienting to name, gaze to faces, joint attention, and affect sharing. [1][2][3][4][5][6] Differences are most evident in the second year of life 7 but some studies have detected signs of ASD before the first birthday. 1,5,8 This early onset pattern is thought to occur in the majority of indiv...

Objective To examine prospectively the emergence of behavioral signs of autism in the first years of life in infants at low and high risk for autism. Method A prospective longitudinal design was used to compare 25 infants later diagnosed with an autism spectrum disorder (ASD) with 25 gender-matched low-risk children later determined to have typical development. Participants were evaluated at 6, 12, 18, 24, and 36 months of age. Frequencies of gaze to faces, social smiles, and directed vocalizations were coded from video and rated by examiners. Results The frequency of gaze to faces, shared smiles, and vocalizations to others were highly comparable between groups at 6 months of age, but significantly declining trajectories over time were apparent in the group later diagnosed with ASD. Group differences were significant by 12 months of age on most variables. Although repeated evaluation documented loss of skills in most infants with ASD, most parents did not report a regression in their child’s development. Conclusions These results suggest that behavioral signs of autism are not present at birth, as once suggested by Kanner, but emerge over time through a process of diminishment of key social communication behaviors. More children may present with a regressive course than previously thought, but parent report methods do not capture this phenomenon well. Implications for onset classification systems and clinical screening are also discussed.

Infant social-communicative behavior, such as gaze to the face of an interactive partner, is an important early developmental skill. Children with autism spectrum disorder exhibit atypicalities in social-communicative behavior, including gaze and eye contact. Behavioral differences in infancy may serve as early markers of autism spectrum disorder and help identify individuals at highest risk for developing the disorder. Researchers often assess social-communicative behavior in a single interactive context, such as during assessment with an unfamiliar examiner or play with a parent. Understanding whether infant behavior is consistent across such contexts is important for evaluating the validity of experimental paradigms and the generalizability of findings from one interactive context/partner to another. We examined infant gaze to the face of a social partner at 6, 9, and 12 months of age in infants who were later diagnosed with autism spectrum disorder, as well as low- and high-risk infants without autism spectrum disorder outcomes, across two interactive contexts: structured testing with an unfamiliar examiner and semi-structured play with a parent. By 9 months, infant gaze behavior was significantly associated between the two contexts. By 12 months, infants without autism spectrum disorder outcomes exhibited higher mean rates of gaze to faces during parent–child play than Mullen testing, while the gaze behavior of the autism spectrum disorder group did not differ by context—suggesting that infants developing autism spectrum disorder may be less sensitive to context or interactive partner. Findings support the validity of assessing infant social-communicative behavior during structured laboratory settings and suggest that infant behavior exhibits consistency across settings and interactive partners.