Prodromal unfolding: the validation of the Schizotypic Syndrome Questionnaire model in a sample of first-episode schizophrenic patients.

Aim: Validation of Van Kampen's Schizotypic Syndrome Questionnaire (SSQ) model of schizophrenic prodromal unfolding. The SSQ model comprises 12 negative, asocial and psychotic-like symptoms that are hypothesized to determine each other in terms of cause and effect.

Method: Use was made of the Interview for the Retrospective Assessment of the Onset of Schizophrenia (IRAOS)-dependent retrospective data assembled in the Mannheim Age-Beginning-Course Study sample of first-episode schizophrenic patients to measure the SSQ symptoms. Both the mean positions of the IRAOS-assessed symptoms on a continuum representing the proportion of total time of pre-psychotic disturbance and the outcome of a series of LISREL analyses conducted on the IRAOS-dependent data were addressed.

Results: Both kinds of data supported the validity of the SSQ model; however, this was after introducing some (relatively minor or demonstrable ineffective) changes in the model as the 'translation' of the SSQ symptoms by means of the IRAOS was not always easy, or proved even impossible in the case of one symptom.

Conclusions: The conclusion seems warranted that the present investigation supports the validity of the SSQ model as a model of pre-psychotic and prodromal unfolding in patients diagnosed as suffering from schizophrenia. From a theoretical perspective, arguments are presented to interpret the SSQ model as a model of the core or principal symptoms of schizophrenia, including their temporal unfolding.