Factor analysis of schizophrenic symptoms and comparison of different rating scales.

This study examines the factor structure of persistent schizophrenic symptoms and compares factors derived from different rating scales. Forty stable chronic schizophrenic patients were assessed for positive and negative symptoms. In factor analysis, 3 factors could be detected: a negative factor which correlated with low drug dose and increased involuntary movements, a thought disturbance/paranoid factor which correlated negatively with extrapyramidal side effects and a delusion/hallucination factor which correlated negatively with involuntary movements. These findings support the existence of a negative factor but only partly the trichotomous division of schizophrenic symptoms. Positive symptom organisation is heterogeneous but thought disorder marks one clear dimension and non-paranoid delusions and hallucinations may mark another. The type of scale used has very significant effects on the findings.