Objectives: Our goal was to understand longitudinal expressive and receptive language during late neurodevelopment in autism, asking two questions: 1) At each time point, does the autism group show different expressive, receptive and total language ability relative to controls? and 2) Is the developmental trajectory of expressive, receptive, and total language ability over time similar or different in the autism and groups?
Methods: Neuropsychological assessments were examined from two time points of testing acquired an average of 8.7 years apart, from 40 high-functioning children and adolescent males with autism (mean age Time 1 = 11.07 years, range = 6-17; mean age Time 2 = 19.95 years, range = 12 - 28) group-matched by age and handedness to 14 typically developing control male children and adolescents (mean age Time 1 = 10.47 years, range = 5-16; mean age Time 2 = 18.66 years, range = 14-26). A diagnosis of autism was obtained using the Autism Diagnostic Interview (ADI) and the Autism Diagnostic Observation Schedule (ADOS). Expressive language ability, receptive language ability and total language ability were measured by the Clinical Evaluation of Language Fundamentals version 3 (CELF- 3). Our comparison employed independent two-sample t-tests, and analysis of covariance.
Results: While controlling for both age and age x group interaction, as expected, language level in the autism group was lower than in controls at the first time point for expressive (p = 0.047) and total language (p = 0.042) abilities. Decreased receptive language ability was found in the autism group compared to the controls at the second time point (p = 0.026). Receptive, expressive and total language standard scores were stable across the age range studied in controls, but significantly improved with age in the autism group.
Conclusions: As expected, mean expressive, receptive and total language standard scores are decreased in high functioning individuals with autism compared to typical development at each time point. Importantly, age-related language ability appears to be increasing at a greater than expected rate in the autism group during late neurodevelopment. To our knowledge, this is one of the first longitudinal studies using the CELF in autism. Greater than expected improvement in the autism group over time suggests that late neurodevelopment, as well as early childhood, is an extremely important time for interventions that target language development in autism. Examination of patterns of individual trajectories of late language development in autism is in progress.
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