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Estimation of premorbid intelligence in schizophrenia
J R Crawford1, J A Besson, M Bremner
1Department of Psychology, University of Aberdeen.
Summary
The National Adult Reading Test (NART) accurately estimates premorbid intelligence in community-dwelling schizophrenia patients. However, NART performance may be affected by the disease in long-stay hospital patients.
Area of Science:
- Neuropsychology
- Psychiatry
Background:
- Estimating premorbid intelligence is crucial for understanding cognitive decline in schizophrenia.
- The National Adult Reading Test (NART) is a commonly used measure for this purpose.
Purpose of the Study:
- To assess the validity of the NART in estimating premorbid intelligence in individuals with schizophrenia.
- To compare NART performance between community-residing and long-stay hospital patients with schizophrenia.
Main Methods:
- Two samples of schizophrenia patients (community-residing and long-stay) were recruited and matched with healthy controls on age, sex, and education.
- Cognitive function was assessed using the Wechsler Adult Intelligence Scale (WAIS) and premorbid intelligence was estimated using the NART.
Main Results:
- Schizophrenia patients in both samples scored significantly lower on the WAIS compared to their matched controls.
- NART-estimated IQ did not significantly differ between community-residing schizophrenics and their controls.
- NART-estimated IQ was significantly lower in long-stay schizophrenia patients compared to their controls.
Conclusions:
- The NART appears to be a valid measure of premorbid intelligence in community-residing individuals with schizophrenia.
- In long-stay schizophrenia patients, lower NART scores may reflect either impaired premorbid intelligence or the effects of the illness on cognitive performance.