Gradations of clinical severity and sensitivity to change assessed with the Beck Depression Inventory-II in Japanese patients with depression.

Knowledge of what constitutes a minimal clinically important difference and change on a psychiatric rating scale is essential in interpreting its scores. The present study examines the Beck Depression Inventory-II (BDI-II), a recently revised successor to the world's most popular self-rating instrument for depression. BDI-II was administered to 85 patients with major depression, diagnosed with DSM-IV along with its severity specifiers. It was again administered to 40 first-visit patients from the original sample when they returned 14 or more days later. The Clinical Global Impression-Change Scale was rated at the same time. All the ratings were done independent of each other. The BDI-II was able to distinguish between all grades of depression severity. An approximate 10-point difference existed between each severity specifier. The BDI-II was also sensitive to change in depression: a 5-point difference corresponded to a minimally important clinical difference, 10-19 points to a moderate difference, and 20 or more points to a large difference. Given the already established high reliability, content validity, construct validity and factorial validity, and the high sensitivity to between-subject differences and within-subject changes demonstrated in the present study, the BDI-II promises to continue to be a leading self-rating instrument to assess depression severity worldwide.