Running Head: PAS-ADD CHECKLIST FACTOR ANALYSIS The Factor Structure of the PAS-ADD Checklist with Adults with Intellectual Disabilities

Background. The PAS-ADD Checklist is designed to screen for likely mental health problems in people with intellectual disabilities (ID). The specificity of recommended subscales derived from diagnostic criteria is unclear; this paper investigates empirically derived subscales. Methods. Informants who had known service users for a median 24 months completed the PAS-ADD Checklist on 1155 adults with ID living in community, residential care and hospital settings in a county in North East England. Results. The sample was randomly divided into two, with all item scores dichotomized. An exploratory principal components factor analysis with varimax rotation was conducted on Subsample A, producing an optimal seven-factor solution. However, a confirmatory factor analysis using this factor structure for Subsample B revealed moderate to poor fit. Further exploratory and confirmatory factor analyses indicated that empirically derived PAS-ADD subscales were inconsistent. Conclusions. Given the inconsistency of empirically derived subscales, we do not recommend using the PAS-ADD Checklist to identify specific types of psychopathology; it may have more utility as a screening tool for general psychopathology and referral for more detailed assessment.