The conviction of delusional beliefs scale: reliability and validity

This study reports on the development of a new measure of delusional belief conviction, the Conviction of Delusional Beliefs Scale (CDBS). Most of the current scales in use assess belief conviction with a single item and primarily reflect the cognitive aspects of conviction. The CDBS represents an improvement over existing scales in that it contains a larger number of test items that can be subjected to psychometric examination. In addition, the CDBS also broadens the concept of belief conviction by incorporating cognitive, emotional, and behavioral items. In the present study, fifty participants with delusions completed the CDBS along with measures of delusional ideation, psychiatric symptomatology, insight, and reading ability. The CDBS showed very good levels of internal consistency and test-retest stability over a six-week period. All of the CDBS items loaded highly on a unitary factor of belief conviction. The CDBS positively correlated with four measures of belief conviction thereby reflecting the convergent validity of the scale. The CDBS was unrelated to other dimensions of delusional ideation, psychiatric symptomatology, insight, and reading ability, which supported the discriminant validity of the scale. The CDBS appears to be a reliable and valid measure of delusional belief conviction that could be used in clinical and research settings.