The Beck Depression Inventory was based on clinical observations of depressed patients. In 21 items the most common depressive symptoms (e.g. sad mood, pessimism, failure, dissatisfaction, guilt, crying, irritability, social withdrawal, inability to resolve, insomnia, appetite loss, etc.) are evaluated.
The total value of the BDI can range from 0 to 63 points. Values below 11 points are considered normal. Values between 11 and 17 points are regarded as a mild to moderate expression of depressive symptoms. Values of 18 and more are considered as a clinically relevant depression.
Since the Beck Depression Inventory in its original version had incomplete coverage of the diagnostic criteria for depression as required in the DSM-IV, in 1996 the BDI-II was developed. In addition to the modification of some items and response options there was a reclassification of the severity.
In the BDI-II values below 13 points are regarded as no or minimal depressive symptoms. Values between 14 and 19 points indicate a mild expression of depressive symptoms, values between 20 and 28 points a moderate severity. Scores between 29 and 63 are regarded as evidence of severe depressive disorder. The completion time for the BDI-II is 10-15 minutes.