Outcome measures in Angelman syndrome.

"Declarations Ethics approval and consent to participateThis study was approved by the medical ethical board of the Erasmus MC (MEC-2020-0489). All legal representatives participants (their legal representatives) signed informed consent. Consent for publicationNot applicable. Competing interestsMCdW is the Erasmus MC study site leader for the Roche Tangelo study, and the hospital received funding for this study. The hospital also received compensation for advice to Roche and Jazz Pharmaceuticals. The department of Child- and Adolescent Psychiatry/Psychology (Erasmus MC) is the Dutch distributer of the Achenbach System of Empirically Based Assessment (ASEBA) measurement instruments, which include the Child Behaviour Checklist (CBCL). The department receives financial compensation for selling the measurement instruments. All other authors have no conflict of interest to declare. Competing interests MCdW is the Erasmus MC study site leader for the Roche Tangelo study, and the hospital received funding for this study. The hospital also received compensation for advice to Roche and Jazz Pharmaceuticals. The department of Child- and Adolescent Psychiatry/Psychology (Erasmus MC) is the Dutch distributer of the Achenbach System of Empirically Based Assessment (ASEBA) measurement instruments, which include the Child Behaviour Checklist (CBCL). The department receives financial compensation for selling the measurement instruments. All other authors have no conflict of interest to declare."

"Funding This study received funding from the Erasmus MC Sophia Foundation (grant number B17-04A) and foundation “Stichting de Merel.”"

"Trial registration Registered d.d. 23-04-2020 under number ‘NL8550’ in the Dutch Trial Register: https://onderzoekmetmensen.nl/en/trial/23075"