Estimation of premorbid intelligence in organic conditions.

The validity of premorbid IQ estimates provided by the National Adult Reading Test (NART) and Vocabulary sub-test of the Wechsler Adult Intelligence Scale were evaluated, by comparison with matched, healthy control subjects, in Korsakoff psychosis, alcoholic dementia, dementia Alzheimer type (DAT), multi-infarct dementia (MID), Huntington's disease, and closed head injury (CHI). There was no significant difference in NART performance between control subjects and the alcoholic dementia, DAT, MID, and CHI groups. Although there appeared to be a decline in NART performance in the Korsakoff and Huntington's groups, it did provide a significantly higher IQ estimate than the Vocabulary sub-test. All clinical groups, with the exception of the CHI group, performed at a significantly lower level than the control group on the Vocabulary sub-test.