Depressive, positive, negative and parkinsonian symptoms in schizophrenia

Objective: Depressive symptoms are common in schizophrenia but their relationship to the positive and negative symptoms of the disorder and to extrapyramidal side-effects remains unclear. Considerable overlap exists between these symptom clusters when rated with traditional clinical rating scales. The aim of this study was to investigate the relationship of depressive to positive, negative and parkinsonian symptoms using the recent adaptation of the Positive and Negative Syndrome Scale (PANSS). Method: The study involved the cross-sectional measurement of symptoms in a sample of community-treated and hospitalized patients with schizophrenia. Structured assessment included the PANSS, Montgomery-Asberg Depression Rating Scale (MADRS) and the Extrapyramidal Side Effects Rating Scale (ESRS). Results: Depressive symptoms were common and correlated with positive and negative symptoms. These correlations were of a similar magnitude using either the original PANSS factor structure or the newer pentagonal model. The overlap between depressive and negative symptoms was limited to certain items in the rating scales and there was a clear separation between these symptom clusters and the other items. Parkinsonian symptoms also correlated with negative symptoms rated with either PANSS model. Conclusion: Use of the pentagonal PANSS model does not improve its capacity to distinguish between depressive and negative symptoms. Positive, negative, parkinsonian and depressive symptoms overlap using common rating scales but there appears to be some separation between these symptom domains when rated with individual scale items rather than total scale scores.