The effect of the use of the International Classification of Diseases 9th revision: upon hospital in-patient diagnoses.

This study compares the diagnostic terminology used for 592 consecutive discharges from a psychiatric unit before and after teaching psychiatric trainees the use of the ICD-9 classificatory system. The results show a marked increase in specificity of diagnostic labels, with a decrease of diagnoses with the term 'not otherwise specified', and an increase in the diagnoses of organic psychoses, paranoid and hebephrenic schizophrenia and depressive neurosis. The implications of this for training about diagnosis, clinical practice and recording of data for national statistics are discussed.