The Beck Depression Inventory is highly reliable in identifying and assessing depressive symptoms, according to the Medical University of South Carolina and a study published by the National Institutes of Health. The BDI has been used for 35 years, it is internally consistent, and its validity has been established.
The BDI was revised to the BDI-II in 1996 to address Diagnostic and Statistical Manual of Mental Disorders depression criteria, according to the study. The BDI-II was translated into German and evaluated in a series of clinical and non-clinical studies. The German BDI-II demonstrated good reliability and validity and replaced the older version of the BDI.