Abstract
This study examines the stability over a five year follow-up of first admission psychiatric diagnoses assigned in New Zealand psychiatric hospitals in 1980 and 1981. Diagnostic stability is a measure of the degree to which psychiatric diagnoses remained unchanged at a later hospital admission. Reasonably high levels of stability were found for the initial diagnoses of substance abuse disorders (86% stable), anorexia nervosa (70%), schizophrenia (67%), and affective disorder (67%). Poor levels of stability were noted for the initial diagnoses of personality disorder (36%), other psychosis (excluding schizophrenia and affective psychosis) (22%), and other neurosis (excluding neurotic depression) (20%). The major trends in diagnostic change are described. Factors influencing diagnostic instability are also examined. For patients with an initial diagnosis of schizophrenia, a change in hospital is found to be the strongest factor causing diagnostic instability, with time between admissions and age at first admission also having a significant influence. The implications of these findings are discussed.