Validity of the depressive dimension extracted from principal component analysis of the PANSS in drug-free patients with schizophrenia

Abstract

Depressive symptoms frequently occur during the course of schizophrenia. This study explored the relationships between the schizophrenia symptomatology and three measures of depression. Eighty-one drug-free inpatients with acute schizophrenia were assessed with the positive and negative syndrome scale (PANSS), the Calgary depression scale for schizophrenia (CDSS), and the Hamilton rating scale for depression (HAM-D). The depressive subscale of PANSS (PANSS-D) was also considered as a third scale for measuring depression. A principal component analysis (PCA) of PANSS items identified five clinical dimensions of schizophrenia called ‘negative’, ‘positive’, ‘anxio-depressive’, ‘excitement’, and ‘disorganisation and others’. Our anxio-depressive dimension (PANSS-ad) was strictly identical with the PANSS-D. Scores on CDSS and HAM-D were highly inter-correlated and highly correlated with the PANSS-ad. Furthermore, while scores on CDSS were correlated only with this dimension, scores at HAM-D were also positively correlated with the negative dimension and negatively correlated with the excitement dimension. In conclusion, our results suggest that PANSS evaluation itself may be sufficient to give a correct approximation of the depression in patients with schizophrenia. However, depression scales are of course needed to assess specifically depressive symptoms in patients with schizophrenia; hence, the CDSS could be a more specific instrument than HAM-D.