Children with neurodevelopmental disorders tend to have more social difficulties than typically developing children. The aim of the current study was to examine parent and teacher-reported effects of age and gender on social functioning in a large clinical sample of children and adolescents with ADHD, autism, or co-occurring ADHD and autism using a cross-sectional study design. This nationwide clinical sample included 2132 Icelandic children and adolescents (35% girls, 65% boys) aged 5-18 years…