Premorbid IQ and schizophrenia

Abstract.

In order to test the hypothesis that acute schizophrenia episodes have a negative impact on cognitive function, 35 consecutive non-abuse schizophrenia outpatients (age < 60) were enrolled in this study. All subjects for whom grades from the 9^th year of the Swedish school system were available, had to complete a comprehensive computerized neuropsychological test session. Symptoms were rated by PANSS and GAF, previous episodes were tallied, and medication was logged. A premorbid cognitive score was calculated on the basis of school grades and validated by comparison with academic career and current cognitive performance (r = 0.56). Half had college level studies or higher, and the overall school grades for the group were above average. PANSS (sum = 59) and GAF [59] ratings as well as medication (M = 230 CPZ units) suggested a moderate symptom level. Two patients had no neuroleptic drugs, 16 had atypical and 17 had conventional neuroleptics. Vocabulary was intact. On average, patients had lost 1 standard deviation (SD) in most cognitive tests but response time slowing amounted to 3.5 SD. There were no differences in cognition between drug types and no correlation with CPZ dose. The number of previous episodes was positively correlated with reaction time prolongation and negatively correlated with short-term verbal memory, consistent with a previous study suggesting that acute episodes cause specific cognitive reduction.