The association between cognitive deficits and different outcomes of schizophrenia

Abstract

Schizophrenia is a disorder with different outcomes. Besides the positive and negative symptoms, cognitive impairment is an important core feature of schizophrenia and often pre-dates the disorder. Cognition has consistently been related to outcome in schizophrenia. Given this finding and the fact that diagnosing and treating schizophrenia as early as possible has better outcome chances, the current study investigated the hypothesis that cognitive performance is associated with two seemingly opposite outcomes: clinical remission and forced hospitalization three years after first assessment. Subjects in the current study were schizophrenia patients not in an active psychosis during cognitive testing (N = 321). The results of the cognitive tests were used as predictor variables for the status of remission or the occurrence of a forced hospitalization in the three years following the cognitive testing. The cognitive tests included were WAIS-III subtests (Digit symbol, Information, Arithmetic, Block Design), Benton Facial Recognition task, Hinting task and the Rey Auditory Verbal Learning task. Besides these cognitive predictors, several relevant covariates (gender, age, education, number of psychotic episodes, duration of illness and amphetamine, cannabis or cocaine intoxication) were analyzed. Two multinomial logistic regression and analyses were conducted with the cognitive tests as independent variables and remission and forced hospitalization as dependent variables in separate models. The results showed that better performance on the verbal tasks (WAIS-III arithmetic score (b=0.17) and the WAIS-III information score (b=0.22)) and less psychotic episodes (b=-0.64) was associated with remission status. Worse performance on the memory task (b=-0.20) and more psychotic episodes (b=0,85) was related to forced hospitalization. This three-year longitudinal study showed that higher verbal IQ is a protective factor and poor memory and higher number of psychotic episodes are risk factors of the outcome of schizophrenia. This suggests that future research on prediction tools for the outcome of schizophrenia should include assessment of verbal IQ and verbal memory.