Symptom dimensions and outcome in schizophrenia.

Since Kraepelin, outcome has been one of the most frequently used criteria for testing the validity of diagnosis in psychiatry. Factor analytic methods have showed, however, that the symptomatology of psychiatric patients can be divided into symptom dimensions, which also correlate with outcome. The aim of the present study was to explore how diagnostic sub-categories and symptom dimensions correlate with outcome in first-episode and chronic patients with schizophrenia. In samples of first-episode schizophrenia patients (n=156) and chronic schizophrenia patients (n=1571), symptom variables were factored and the five symptom dimensions obtained were correlated with outcome variables. In both samples, symptom dimensions were more powerful in explaining variance of outcome than categorical sub-diagnoses. Thus, a dimensional approach seems to be valuable not only in describing the illness picture, but also in predicting outcome in schizophrenia.