Intellectual deterioration and personality decompensation in schizophrenia.

The Army General Classification Test (AGCT) and the MMPI were administered to schizophrenic inpatients (N = 50) with initially high (mean standard score = 115) and low (77) intelligence at two timepoints separated by an average of 14 years. The Arithmetic scores of the more intelligent group declined significantly with time, but significant changes did not appear on the Vocabulary or Spatial Aptitude scores of that group. No significant mean changes appeared in the low-IQ sample. The high-IQ group's Arithmetic section deterioration resulted from an increased error rate, not a drop in speed. No changes beyond those attributable to chance appeared on the MMPI scales. The results suggest that an intellectual decline limited to certain skills and to a subset of subjects occurs in schizophrenia and that the deterioration is not attributable to personality decompensation as defined by the MMPI. Because these findings appear to contrast with most previous research in this area, they should be considered tentative until confirmed by independent studies.