Prader-Willi syndrome and psychotic symptoms: 2. A preliminary study of prevalence using the Psychopathology Assessment Schedule for Adults with Developmental Disability Checklist

The Psychopathology Assessment Schedule far Adults with Developmental Disability (PAS-ADD) checklist was used to screen for psychotic symptoms among people with Prader-Willi syndrome (PWS) aged 16 years and over. The scoring instructions for the PAS-ADD checklist were modified to take account of knowledge about the behavioural phenotype of PWS. Using modified scoring, 6.3% of the 95 people for whom checklists were completed had a possible psychotic disorder in the month before the assessment was made. The results should be treated as a crude estimate of the prevalence of psychotic symptoms associated with PWS in adult life in view of potential biases in the sample reported. These findings tend some support to the hypothesis that PWS has a non-chance association with psychotic symptoms and that the association is not entirely accounted for by the increased prevalence of psychosis associated with intellectual disability.