Abstract: Types of Rating Scale The value of this one, and its limitations, can best be considered against its background, so it is useful to consider the limitations of the various rating scales extant. They can be classified into four groups, the first of which has been devised for use on normal subjects. Patients suffering from mental disorders score very highly on some of the variables and these high scores serve as a measure of their illness. Such scales can be very useful, but have two defects: many symptoms are not found in normal persons; and less obviously, but more important, there is a qualitative difference between symptoms of mental illness and normal variations of behaviour. The difference between the two is not a philosophical problem but a biological one. There is always a loss of function in illness, with impaired efficiency. Self-rating scales are popular because they are easy to administer. Aside from the notorious unreliability of self-assessment, such scales are of little use for semiliterate patients and are no use for seriously ill patients who are unable to deal with them. Many rating scales for behaviour have been devised for assessing the social adjustment of patients and their behaviour in the hospital ward. They are very useful for their purpose but give little or no information about symptoms. Finally, a number of scales have been devised specifically for rating symptoms of mental illness. They cover the whole range of symptoms, but such all-inclusiveness has its disadvantages. In the first place, it is extremely difficult to differentiate some symptoms, e.g., apathy, retardation, stupor. These three look alike, but they are quite different and appear in different settings. Other symptoms are difficult to define, except in terms of their settings, e.g., mild agitation and derealization. A more serious difficulty lies in the fallacy of naming. For example, the term "delusions" covers schizophrenic, depressive, hypochrondriacal, and paranoid delusions. They are all quite different and should be clearly distinguished. Another difficulty may be summarized by saying that the weights given to symptoms should not be linear. Thus, in schizophrenia, the amount of anxiety is of no importance, whereas in anxiety states it is fundamental. Again, a schizophrenic patient who has delusions is not necessarily worse than one who has not, but a depressive patient who has, is much worse. Finally, although rating scales are not used for making a diagnosis, they should have some relation to it. Thus the schizophrenic patients should have a high score on schizophrenia and comparatively small scores on other syndromes. In practice, this does not occur. The present scale has been devised for use only on patients already diagnosed as suffering from affective disorder of depressive type. It is used for quantifying the results of an interview, and its value depends entirely on the skill of the interviewer in eliciting the necessary information. The interviewer may, and should, use all information available to help him with his interview and in making the final assessment. The scale has undergone a number of changes since it was first tried out, and although there is room for further improvement, it will be found efficient and simple in use. It has been found to be of great practical value in assessing results of treatment.