Prader–Willi syndrome, compulsive and ritualistic behaviours: the first population-based survey

Obsessive-compulsive disorder has been reported in association with Prader-Willi syndrome. To report the nature and prevalence of compulsive and similar symptoms associated with Prader-Willi syndrome in a population ascertained as completely as possible. Attempted complete ascertainment of people with Prader-Willi syndrome in eight English counties. Administration of standardised rating scales and a structured interview. Comparison with people with learning disability and high body mass indices. Prader-Willi syndrome was associated with high rates of ritualistic behaviours, such as the need to ask or to tell something, insistence on routines, hoarding and ordering objects and repetitive actions and speech, compared with the control group, and was negatively correlated with IQ and socialisation age. Typical obsessive-compulsive symptoms, such as checking, counting and cleaning compulsions or obsessional thoughts, were not found. Ritualistic and compulsive behaviours occur more frequently in association with Prader-Willi syndrome than among people with intellectual disability and significant obesity.