The goal of this observational cross-sectional study is to establish the prevalence of autism spectrum disorder in children and adolescents with Angelman syndrome. The main questions it aims to answer are: * which clinical variables differentiate AS patients with and without Autism Spectrum Disorder between genetics, epilepsy, pharmacotherapy, behavioural problems, parenting style and parents' perceived stress. * which clinical variables differentiate parenting styles and levels of perceived stress. Data from neuropsychological, speech therapy and physiotherapeutic assessments are collected during regular clinical follow-ups, regarding: cognitive development (Bayely Scales of Infant Development-III, Cognitive Scale) and adaptive behaviour; Autism and Autism Spectrum Disorder (Autism Diagnostic Observational Schedule-2); parental stress and parenting styles; social-communicative skills; motor development.