The core symptoms of depression in medical and psychiatric patients.

The internal consistency of the Beck Depression Inventory (BDI) is assessed in 335 randomly selected medical inpatients, and in another sample of 101 depressed psychiatric inpatients with 104 interviewed normals. The data for the two samples were analyzed separately using a latent trait model. The analysis confirms that the BDI measures a single underlying dimension of depressive severity for both patient samples. Fourteen symptoms discriminate well for severity of depression in the psychiatric-normal sample, seven symptoms in the medical sample, and six symptoms in both samples. The latter six symptoms (suicidal ideation, sense of failure, sense of punishment, loss of social interest, indecision, and dissatisfaction) may represent criteria for depressive severity that are not confounded by the presence of physical illness or the attendant distress.