The Beck Depression Inventory (BDI) is a questionnaire that is used to assess whether a person displays symptoms of depression. The BDI includes 21 questions, which assign a numerical value to each possible response. For each question, the test taker chooses one of several options that most closely fits their circumstances, with the following as a specific example:

• 0: I do not feel sad.
• 1: I feel sad.
• 2: I am sad all the time and can’t snap out of it.
• 3: I am so sad and unhappy that I can’t stand it.

The numbers associated with the chosen option for all questions are added up to form a total score ranging from 0 to 63, with higher scores denoting greater depression symptomatology. The BDI can be used to screen for depression, although a clinician needs to consider a person’s BDI score in conjunction with their medical history in order for a depression diagnosis to be made.

The minimum clinically significant difference in BDI ( the smallest change in BDI that is perceived as important) is an area of active investigation. Some research suggests that a decrease of 5 to 11 points is clinically significant,^[1] whereas other research suggests that a relative decrease of approximately 17.5%–30% is a better metric of clinical significance.^[1]