Pathways to schizophrenic psychosis: a LISREL-tested model of the unfolding of the schizophrenic prodrome.

In this article a literature-based model (the Schizotypic Syndrome Questionnaire [SSQ] model) is presented that gives a description of the temporal unfolding of the schizophrenic prodrome. As a guiding principle for the selection of the symptoms in the model, the hypothesis was held that the main prodromal features determine each other in terms of cause and effect. Furthermore, the developmental pathways between the symptoms were not allowed to be in conflict with the usual observation that negative symptoms precede psychotic-like ones nor--at least in broad outline--with J.P. Docherty, D.P. van Kammen, S.G. Siris, and S.R. Marder's (1978) description of the various onset stages in the development of a schizophrenic psychosis. For the definitive version of the SSQ model, 12 symptoms were selected (e.g., affective flattening, suspicion, and delusional thinking). After specifying the paths to be estimated, the model was examined in two randomly drawn samples from a total community-based sample of 771 normal subjects and in the total sample itself, in each case resulting in adequate fit values. Moreover, all postulated pathways were found to be significantly different from zero. The use of a normal sample was based on the continuum hypothesis. Given the present-day discussions concerning the tenability of the schizophrenia concept, the model's implications with respect to that issue are particularly emphasized. Furthermore, the concept of the schizophrenia prodrome itself is critically discussed.