The Beck Depression Inventory (BDI) is a widely used self-report questionnaire designed to assess the severity of depression in individuals. Developed by Dr. Aaron T. Beck in the 1960s, it consists of 21 multiple-choice questions that cover various symptoms of depression, such as sadness, hopelessness, and changes in sleep patterns. Each item is scored on a scale, allowing for a quantifiable measure of depressive symptoms. The BDI is commonly used in clinical settings, research, and mental health assessments. It helps healthcare professionals identify the presence and intensity of depression, guiding treatment decisions. The inventory is recognized for its reliability and validity, making it a valuable tool in understanding mental health.