Beck Depression Inventory (BDI) The Beck Depression Inventory (BDI) is a widely used and well-established self-report questionnaire designed to assess the severity of depression. The BDI was developed by Dr Aaron T. Beck in 1961 and has since undergone several revisions, with the most recent version, the BDI-II, being published in 1996. The BDI is a 21-item questionnaire that measures a wide range of depression symptoms, such as sadness, hopelessness, guilt, and tiredness. Each item is rated on a 4-point scale, with higher scores indicating a greater severity of depression. The BDI has been found to have high reliability and validity, and has been widely used in both clinical and research settings. One of the strengths of the BDI is its brevity. The questionnaire can be administered in just a few minutes and provides a quick and easy way to assess the severity of depression. The BDI has also been found to be useful in differentiating between different subtypes of depression, such as