IDENTIFYING SUBTYPES OF SCHIZOPHRENIA BY CLUSTER ANALYSES

The existence of two subtypes of schizophrenia (positive and negative) is well established. The evidence in favor of other subtypes, particu larly a disorganized subtype, is still the subject of some debate. The aim of the study reported in this article is to investigate the possi bility of further subtypes of schizophrenia by applying a particular m ethod of cluster analysis to a particular set of data. Ward's method o f cluster analysis was applied to the Positive and Negative Syndrome S cale (PANSS) scores of 138 patients, defined as having schizophrenia b y one of four diagnostic criteria. The validity of the cluster solutio n was assessed both by examining differences between clusters on a num ber of clinical characteristics recorded for each patient and by compa ring the results obtained from the PANSS with those derived from a clu ster analysis using two other instruments (the Scale for the Assessmen t of Negative Symptoms and the Scale for the Assessment of Positive Sy mptoms). Results from the cluster analysis suggest the existence of at least four subtypes of schizophrenia: positive, negative, mixed, and disorganized. A fifth subtype includes patients with few symptoms, sug gesting the simple schizophrenia named by Bleuler. Evidence for the va lidity of these subtypes was provided by the differences observed betw een the clusters on a number of clinical characteristics and by the si milarity of the cluster solution obtained from the different instrumen ts. In conclusion, the negative-positive dichotomy in schizophrenia is an oversimplification, and the existence of a more complex structure needs to be taken into account in future research.