PRINCIPAL COMPONENTS AND FURTHER POSSIBILITIES WITH THE PANSS

At the end of the last century, Hughlings-Jackson suggested that posit ive and negative syndromes should be kept apart in psychotic disorders . When the concepts of dementia praecox and schizophrenia were introdu ced by Kraepelin and Bleuler, emphasis was laid on the negative sympto ms, regarded as fundamental. After the introduction of the ''first ran k symptoms'' by Schneider emphasis switched to the positive symptoms i n schizophrenia and these symptoms were included in most diagnostic cr iteria. In the 1980s Andreasen and Crow suggested a dichotomy into pos itive and negative syndromes in schizophrenia. Kay and co-workers intr oduced a Positive And Negative Syndrome Scale (PANSS) for schizophreni a. In the original studies satisfactory construct validity and inter-r ater reliability were demonstrated. However, in studies outside the US A a high construct validity was found for the negative scales but not for the positive and general psychopathology scales. Furthermore, the inter-rater reliability of the negative scale was a problem. After int roduction of the Structured Clinical Interview for the PANSS (SCI-PANS S) the inter-rater reliability increased for all three scales. In an e arly study Kay and Sevy found seven factors in a principal component a nalysis of the PANSS and suggested a four factor pyramidical model. La ter principal component analyses by Lepine, Peralta et al. and Kawasak i et al. suggested that the four factor model was an oversimplificatio n and Lindstrom and von Knorring suggested a five factor pyramidical m odel. A similar model was later suggested by Bell et al. after a reana lysis of the original series of Kay and Sevy. In short- and long-term studies of the new balanced serotonin 5-HT2-dopamine D-2 antagonist, r isperidone, it has been demonstrated that all five factors, the positi ve, the negative, the excited, the anxious/depressive and the cognitiv e, are sensitive to changes induced by means of psychopharmacological drugs. Thus the five factor model of schizophrenia seems to be an inte resting tool when new, selective, psychopharmacological drugs are to b e evaluated and when differences in clinical profiles are sought betwe en different drugs.