A technique for studying psychiatric morbidity in in-patient and out-patient series and in general population samples.

Many surveys of general populations have suggested a high untreated psychiatric morbidity, vairously referred to as mental illness, pre-clinical neurosis, minor neurosis, untreated depression, etc. An Index of Definition psychiatric disorders is described which incorporates cut-off points on the basis of symptoms rated in the Present State Examination. Eight degrees of definition are specified. At the "borderline disorder" level and above, disorders are sufficiently well defined to apply the CATEGO program of clinical classification. This procedure enables in-patients, out-patients and samples of the general population to be compared. Data from surveys in south-east London are presented in order to illustrate the technique. The main conclusion at this stage is that it is possible to identify, by strictly defined and repeatable procedures, a substantial proportion of people in the general population who have "borderline disorders" that can be tentatively classified in terms of the ICD. Whether it is clinically useful to do so requires further investigation. It is also suggested that techniques of this kind can be scientifically useful in comparing the level of morbidity in various populations, both referred and non-referred, and in testing theories concerned with the causes and treatment of various types of psychiatric disorders.