Prof Forbes conceptualized and designed the study, was responsible for obtaining funding, reviewed and revised the manuscript, and critically reviewed the manuscript for important intellectual content regarding aspects of gastroenterology. Dr Ravikumara conceptualized and designed the study, was responsible for obtaining funding, reviewed and revised the manuscript, and critically reviewed the manuscript for important intellectual content regarding aspects of gastroenterology. A/Prof Jacoby conceptualized and designed the study, was responsible for obtaining funding, provided specialist statistical support, and reviewed and revised the manuscript. Ms Bourke collected data for the study, and critically reviewed the manuscript for important intellectual content regarding aspects of intellectual disability. Dr Srasuebkul reviewed and critically reviewed the manuscript for important intellectual content regarding aspects of intellectual disability. Prof Trollor conceptualized and designed the study, was responsible for obtaining funding, reviewed and revised the manuscript, and critically reviewed the manuscript for important intellectual content regarding aspects of intellectual disability. Dr Wilson conceptualized and designed the study, was responsible for obtaining funding, reviewed and revised the manuscript, and critically reviewed the manuscript for important intellectual content regarding aspects of pediatric medicine. Prof Nagarajan conceptualized and designed the study, was responsible for obtaining funding, reviewed and revised the manuscript, and critically reviewed the manuscript for important intellectual content regarding aspects of pediatric medicine. A/Prof Jenny Downs conceptualized and designed the study, was responsible for obtaining funding coordinated and supervised linked data collection, reviewed and revised the manuscript and was the principal investigator of the research. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.