Assessment of anxiety in children and adolescents: A comparative study on the validity and reliability of the Spence Children's Anxiety Scale in children and adolescents with anxiety and Autism Spectrum Disorder.

•The factor structure of the SCAS-P is not identical in groups of young people with anxiety and ASD.•The relationship between SCAS-P items and factors differs across anxious and ASD groups.•ASD impacted on three of the six factors and eleven of the thirty-eight items of the SCAS-P.•Results on the SCAS-P in children with ASD need to be interpreted with caution.