The Beck Depression Inventory (BDI) is a series of questions developed to measure the intensity, severity, and depth of depression in patients with psychiatric diagnoses.

The inventory was developed in 1961 by Aaron T. Beck and later revised in 1978 as the BDI-1A. A second version of the inventory (BDI-II) was developed to reflect revisions in the DSM-IV-TR. It has been extensively tested for content validity, concurrent validity, and construct validity.

The long form of the BDI is composed of 21 questions or items, each with four possible responses. Each response is assigned a score ranging from zero to three, indicating the severity of the symptom. Items 1 to 13 assess symptoms that are psychological in nature, while items 14 to 21 assess more physical symptoms.
It usually takes between five and 10 minutes to complete as part of a psychological or medical examination.

The sum of all BDI item scores indicates the severity of depression.
The test is scored differently for the general population and for individuals who have been clinically diagnosed with depression.
- For the general population, a score of 21 or over represents depression.
- For people who have been clinically diagnosed, scores from 0 to 9 represent minimal depressive symptoms, scores of 10 to 16 indicate mild depression, scores of 17 to 29 indicate moderate depression, and scores of 30 to 63 indicate severe depression.

A version designed for use by primary care providers (BDI-PC) is composed of seven self-reported items, each correlating to a symptom of major depressive disorder.

Adapted from Encyclopedia of Mental Disorders. Beck Depression Inventory. Internet. Accessed on October 21, 2011.