National British Psychological Society Department of Health Down’s Syndrome Association Foundation for People with Learning Disabilities The Health Foundation International Association for the Scientific Study of Intellectual Disabilities (IASSID) International Prader-Willi Syndrome Organisation Medical Research Council Mental Health Research Network National Autistic Society The Prader-Willi Syndrome Association (UK) Prader-Willi Syndrome Association (USA) The Royal College of Psychiatrists Society for the Study of Behavioural Phenotypes (SSBP) Journals Journal of Intellectual Disability Research (JIDR) Local Department of Psychiatry Developmental Psychiatry MRC Cognition and Brain Science Unit NIHR CLAHRC East of England Cambridgeshire and Peterborough NHS Foundation Trust