[A four-dimensional model of chronic schizophrenia based on the factorial structure of the Positive and Negative Syndrome Scale (PANSS). A study of a group of 153 chronic schizophrenic patients and comparison with the factorial structure of the BPRS].Encephale. 1997 Jan-Feb; 23(1):10-8.E
The aim of the study is to explore the latent dimensions in chronic schizophrenia using factorial analysis methods. 153 subjects (89 males, 64 females) with a mean age of 38.83 years (sd = 10.15) meet the RDC criteria for chronic schizophrenia and were included in the study. They were 127 inpatients and 26 outpatients and the mean duration of the illness since the first psychotic episode was 14.69 years (sd = 9.64). The majority of the schizophrenics received antipsychotic treatment with a mean dose (in chlorpromazine-equivalent) of 401.86 mg (sd = 368.13). The schizophrenics were rated using the French versions of the Positive and Negative Syndrome Scale (PANSS) and the Brief Psychiatric Rating Scale (BPRS). Two successive principal components analyses (PCA) were carried out on the correlation matrix of the 30 PANSS and 18 BPRS items. The numbers of factors were limited using several guidelines : eigenvalues higher than 1, screen test and the parallel analysis of Horn. Then an orthogonal equamax rotation was made and the saturation value was chosen using and ad-hoc paradigm. The results have shown a four-factors solution for the PANSS with the following factors : negative, positive-hostility, disorganization-impulsivity, depressive-anxious. The composition of the four preceding factors was respectively : negative [N1, N2, N3, N4, N6, N7, G7, P4 (-)]; positive-hostility (P1, P2, P3, P5, P6, P7, G8, G9, G12, G15, G16); disorganization-impulsivity (G5, G10, G11, G13, G14, N5); depressive-anxious (G1, G2, G3, G4, G6). The ACP of the BPRS have shown a three factors solution (positive-disorganization, negative, depressive-anxious). The factorial structure of the PANSS was discussed with the different studies. Our results confirm the division of the productive symptomatology into two components, delusions-hallucinations and cognitive (disorganization). Moreover depressive and negative symptomatology constitute two separate dimensions. Contrary to the others studies we did not find an excited component, the corresponding items were found in the positive and disorganization factors. The inclusion of solely chronic schizophrenics could explain the lack of the excited component. Our data in chronic schizophrenia allow us to propose a four-dimensional model explaining the symptomatology of this disease.