Autism is currently viewed as a spectrum condition including strikingly different severity levels. IQ is consistently described as one of the primary aspects of the heterogeneity in autism. To investigate the possibility of more than one distinct subtype of autism based on IQ, both latent class analysis and taxometric methods were used to classify Mullen IQ scores in a sample of children with autism spectrum disorder (N=456). Evidence for multiple IQ-based subgroups was found using both methods. Groups differed in level of intellectual functioning and patterns of verbal versus nonverbal ability. Results support the notion of distinct subtypes of autism which differ in severity of intellectual ability, patterns of cognitive strengths and weaknesses, and severity of autism symptoms.

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