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Does operational diagnosis of schizophrenia significantly impact intellectual deficits in psychotic disorders?
H Kitamura1, T Shioiri, M Itoh
1Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan. kitamura@med.niigata-u.ac.jp
Background:
Evidence suggests that, as a group, patients with schizophrenia have intellectual deficits that may precede the manifestation of psychotic symptoms; however, how successfully intelligence tests are able to discriminate schizophrenia from other psychotic disorders has yet to be investigated in detail.
Methods:
Using Wechsler Adult Intelligence Scale-Revised (WAIS-R) data for 55 inpatients with schizophrenia and 28 inpatients with non-schizophrenic psychotic disorders (NSPD) (schizophreniform disorder, brief psychotic disorder, delusional disorder, psychotic disorder due to a general medical condition, and psychotic disorders not otherwise specified), intelligence performance was compared between schizophrenia and NSPD and among different subtypes of schizophrenia.
Results:
There were no significant differences in intelligence quotient (IQ), verbal IQ (VIQ) and performance IQ (PIQ) discrepancy, and subtest scores of WAIS-R between the patients with schizophrenia and those with NSPD. These diagnostic groups were not discriminated well by any WAIS-R variables. Schizophrenia patients with prominent negative symptoms, on the other hand, had a significantly larger IQ discrepancy (VIQ > PIQ) than those without prominent negative symptoms and NSPD patients. Intelligence performance in schizophrenia did not differ with respect to diagnostic subtypes and longitudinal courses.
Conclusions:
The current study failed to show diagnostic usefulness of WAIS-R in discriminating schizophrenia and other psychoses. A diagnosis of schizophrenia does not significantly impact intellectual deficits in psychotic disorders.
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