RELIABILITY AND VALIDITY OF THE YALE-BROWN OBSESSIVE-COMPULSIVE SCALE

The reliability and validity of the Yale-Brown Obsessive-Compulsive Sc ale were examined according to a multi-trait multi-method approach in a sample of 54 outpatients with obsessive-compulsive disorder (OCD). I nternal consistency was acceptable but was improved by deletion of ite ms concerning resistance to obsessions and compulsions. Inter-rater re liability was excellent, but test-retest reliability over an average i nterval of 48.5 days was lower than desirable. The YBOCS demonstrated good convergent validity with most other measures of OCD, but divergen t validity vis a vis depression was poor. Analyses of new items assess ing avoidance and the duration of obsession-free and compulsion-free i ntervals indicated that only the avoidance rating added meaningfully t o the full scale score. In future research the authors recommend delet ion of the resistance items and inclusion of the avoidance item to yie ld a revised 9-item YBOCS total score.