IQ deficit in schizophrenia: a test of competing theories.

ABSTRACT

This study tested competing interpretations of IQ deficit in schizophrenic patients. One interpretation (concomitancy hypothesis) holds that IQ loss is a product of schizophrenic symptoms and is remedied as the symptoms remit. The second (prodromal hypothesis) holds that IQ deficit preceeds and facilitates the development of schizophrenic disorder and is not remedied with symptom remission. The IQs of schizophrenic patients were obtained before and three times after hospital treatment. All mean IQs fell within average limits and did not increase significantly after treatment although test-retest correlations suggested slight disruption of IQ in the morbid state. Remitting cases did not differ significantly from nonremitting cases. Paradoxically, chronic patients earned slightly higher IQs than acute patients. The findings are interpreted as providing some support for both interpretations of schizophrenic IQ deficit. It is concluded that the specific IQ tests used and the nature of the patient samples tested will have a significant bearing on which hypothesis is supported in individual studies of schizophrenic IQ deficit.