Concurrent and predictive validity of components of disordered thinking in schizophrenia

Although the various manifestations of disordered thought have played a central role in diagnostic and theoretical considerations of schizophrenia, such symptoms have not been found specific to schizophrenia, and at best have shown weak relations to outcome. As part of a 7-year followup study of a sample of young, acute, psychotic inpatients, we explored the hypothesis that despite these poor results there might be particular components of disordered thought that might have prognostic utility and be able to discriminate narrowly defined schizophrenics. Using extant symptom scales as our models, we constructed five internally consistent scales of disordered thought from behavioral ratings made using the Psychotic Inpatient Profile--Poverty of Speech, Attentional Impairment, Incoherence, Delusions, and Hallucinations. We tested the ability of these scales to predict various aspects of outcome adaptation including outcome diagnosis. In general, the Attentional Impairment scale demonstrated the best prognostic utility, predicting poorer outcome in several domains. Paradoxically, patients diagnosed by Research Diagnostic Criteria (RDC) as definite schizophrenic at outcome had been rated as showing less attentional impairment than probable and nonschizophrenics. An examination of the pattern of correlations between Attentional Impairment and performance on cognitive tasks suggested that attentional difficulties may be related to different underlying cognitive processes in those diagnosed schizophrenic and nonschizophrenic at outcome by RDC.