Principal component analysis of the Swedish version of the Positive and Negative Syndrome Scale for schizophrenia

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Abstract
With permission from the late Dr. S. Kay, the Positive and Negative Syndrome Scale (PANSS) for schizophrenia has been translated into Swedish. In an earlier study, construct validity and inter-rater reliability have been demonstrated. In the present study, a principal component analysis was made on a series of 120 schizophrenic patients rated by means of the PANSS. As in earlier studies by Kay and Sevy and by Peuskens, a Negative, an Excited, a Positive, and a Depressive factor were found. These factors were very similar to those earlier described. However, the Depressive factor included important contributions from anxiety-related items and is best explained as an Anxious/Depressive factor. Furthermore, an important Cognitive factor was found. This factor has also been seen in the seven-factor results found by Kay and Sevy and by Peuskens but has been omitted in the final four-factor pyramidic model. From the results of the present study, however, it seems reasonable to modify and extend the pyramidic model with a five-factor model, including a Cognitive factor. With this five-factor model 70% of the variance is explained in the present principal component analysis. In the original pyramidic model suggested by Kay a relationship was hypothesized between the syndrome factors and the subgroups of schizophrenia. Such a relationship is not supported by the results of the present study.