The Hamilton Depression Rating Scale (HDRS); changes in scores as a function of training and version used.

The co-existence of different versions of the Hamilton Depression Rating Scale (HDRS) may introduce a source of error in depression research. In a training procedure, based on 16 videotapes, over 900 scores were used to investigate differences between two prominent versions. The HDRS published by Bech et al. in 1986 produced significantly lower total scores than the original HDRS presented by Hamilton in 1960. Previous experience of the raters, both in psychiatry and in the use of the scale, increased the scores in a nonsignificant way. During the training raters' scores increased significantly. These effects were small, one point each in the total scores, but they were consistent throughout our material. In depression research, training procedures and the exact version of the scales used should be specified.