Dimensionality of depression in acute schizophrenia: a methodological study using the Bech-Rafaelsen Melancholia...

Despite the great clinical importance of depressive symptoms in schizophrenia there is a lack of studies on the assessment and evaluation of depression in acutely psychotic patients. For the Bech-Rafaelsen Melancholia Scale (BRMES), among other advantages, the concept of unidimensionality was confirmed in patients with major depression by different methodological approaches including Rasch analysis. The present evaluation was designed to investigate the scale properties of the BRMES in acutely schizophrenic patients with particular emphasis on the dimensionality of the scale. Three different statistical approaches were used: principal component analysis in combination with computer simulation, polytomous Rasch analysis using advanced latent trait and latent class models and confirmatory factor analysis (CFA) by means of linear structure model approaches. The statistical methods were applied to BRMES baseline data of 132 acutely schizophrenic patients with predominantly positive symptoms participating in a multi-center pharmacological trial. The different methodological approaches revealed converging results indicating: (1) a substantial proportion of acutely ill schizophrenic patients showed depressive symptoms; (2) the hypothesis of unidimensionality of the BRMES had to be rejected for the sample of acutely schizophrenic patients and (3) a three-factorial model of depressive symptoms as measured by the BRMES ('retardation', 'depressive core symptoms', 'unspecific depressive symptoms') yielded the best fit of the present data. Depression in acutely psychotic patients has to be considered rather as a heterogeneous construct than as a well-defined syndrome. The differentiation of depressive symptomatology should facilitate treatment evaluation and help to clarify relationships between different symptom classes in further studies.