The present study employed the Disability Assessment Schedule (DAS) to assess problem behaviors in a large sample of adults with ID (N=568) and evaluate the psychometric properties of this instrument. Although the DAS problem behaviors were found to be internally consistent (Cronbach's α=.87), item analysis revealed one weak item ('Objectional habits') with item-total biserial correlation of only .20. An exploratory factor analysis revealed two main factors. The first factor consisted of items relating to disruptive/distractive problems. The second factor consisted of items relating to antisocial/delinquent problems. Disruptive/distractive problems were specifically associated with low ID level. Antisocial/delinquent behaviors were specifically associated with male gender, schizophrenia, hospital admission and troubles with police. For patients who had both disruptive/distractive problems and antisocial/delinquent behaviors, personality disorders and autism were more frequent, where as anxiety and depression were less frequent. On the basis of the obtained results, two new DAS subscales for assessing challenging behavior were proposed. Both subscales had good levels of internal consistency, as well as face and criterion validity. Overall, the new DAS subscales were shown to have acceptable psychometric properties and have therefore potential for use in both research and clinical practice.
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