Illness duration and neuropsychological impairments in schizophrenia

This study aims to verify whether cognitive disturbances in schizophrenic patients are associated with illness duration, and to examine the influence of other covariates on neuropsychological disturbances. Sixty-nine consecutive admissions of schizophrenic patients (DSM-III-R, APA, 1987) were included to an acute psychiatric unit. Patients were evaluated by a semistructured interview and assessed with the Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS). A wide neuropsychological battery, adapted to Spanish, was used. Variables were transformed to z-scores when their distribution was normal, or to log-values in the case of non-normal distributions. Pearson's correlation coefficients with a Bonferroni correction showed strong relationships between illness duration and cognitive performance in neuropsychological tests on visuomotor processes and delayed visual memory. In order to examine the influence of potential covariates on neuropsychological disturbances, stepwise multiple regression procedures were performed with each neuropsychological measure as a dependent variable, and years of education, age, gender, neuroleptic does in chlorpromazine equivalents, biperidene doses and illness duration as independent variables. The longer the illness duration, the poorer the performance on visuomotor process and delayed visual memory tasks. Moreover, the neuropsychological disturbances associated with illness duration were different from those related to aging, educational background, gender and treatment status. These findings suggest the existence of a relationship between cognitive decline in visuomotor and delayed visual memory functions and the length of schizophrenic illness.