Relationships between sluggish cognitive tempo (SCT) and age and IQ were investigated in children with autism and/or ADHD covering broader age and IQ ranges than in previous studies. Mothers rated 1436 children with autism and 1,056 with ADHD (2-17 years, IQs 9-149) on Pediatric Behavior Scale SCT items. Increasing age correlated with SCT in the autism, ADHD-Combined, and ADHD-Inattentive samples. SCT prevalence rates were 22% preschool, 29% early childhood, 41% late childhood, and 50% adolescence. Correlations between IQ and SCT were small and negative. SCT was lowest in children with above average intelligence. Children referred for autism and ADHD should be assessed for SCT, irrespective of IQ and age, given SCT's high prevalence and association with social and academic impairment.
Keywords: ADHD; Age; Autism; IQ; Sluggish cognitive tempo (SCT).
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