Level of intellectual functioning predicts patterns of associated symptoms in school-age children with autism spectrum disorder.

The relation between level of intellectual functioning and risk for associated symptoms in children with autism spectrum disorder (ASD) was investigated. Cognitive ability and associated symptoms were assessed directly and/or via parent report in 74 children with ASD at 6 and 9 years of age. Participants were classified as lower and higher functioning using Nonverbal and Verbal IQ and Communication scores on the Vineland at age 6. Children with higher functioning at age 6 displayed increased internalizing symptoms by age 9, whereas children with lower functioning displayed higher hyperactivity, attention problems, and irritability by age 9. Results suggest that level of intellectual functioning may be a risk factor for different patterns of associated symptoms by later childhood.