A cross-syndrome approach to the social phenotype of neurodevelopmental disorders: Focusing on social vulnerability and social interaction style

•Heightened social vulnerability is evident across multiple neurodevelopmental disorders.•The limitation of IQ to explain social vulnerability is shown by a cross-syndrome approach.•Atypical social interaction styles vary within and across neurodevelopmental groups.•Social interaction styles make a unique contribution to heightened social vulnerability.•Social phenotypes are best understood as distributed across diagnostic boundaries.