Neuropsychological assessment in schizophrenic patients treated with haloperidol or clozapine

Objective: The purpose of this study was to examine whether there are differences between two schizophrenic patient groups treated with haloperidol or clozapine, on measures of cognitive functions. The hypothesis of the study was that the patients treated with clozapine would demonstrate higher performance on neurocognitive functions than those treated with haloperidol. Method: Fiftytwo patients who met DSM-IV criteria for schizophrenia were included in this study. Thirthyseven patients have been treated with haloperidol and 15 patients with clozapine for at least a two-week period. Demographic variables were obtained by interviewing the patients and their relatives. These variables included age, gender, educational status, duration of illness, number of admissions, and type and duration of past and present treatment. A comprehensive neurocognitive test battery was designed to evaluate a broad range of cognitive domains and was administered to all subjects. The battery included 11 tests. These assessments were focused on measures of attention, learning and memory, executive functions, language, and visuospatial perception. Obtained variables of two treatment groups were compared by using Mann-Whitney U test and Chi- square test. Results: In terms of neuropsychological functioning, there were significant differences between two treatment groups. The patients under clozapine treatment performed significantly better than those under haloperidol treatment on measures of learning and memory, executive functions, and visuospatial perception. In clozapine group when compared to haloperidol group, while immediate learning, total learning, and highest learning scores of Auditory Verbal Learning Test were significantly higher and average number of trials for exact learning was significantly lower(p=0,03& p=0,05). The number of correct responses on Raven Progressive Matrices Test and on Benton Judgment of Line Orientation Test were also significantly higher(p=0,01 & p=0,02) in clozapine group. These detected differences were found to be powerful enough. Conclusion: In the present study, patients under clozapine treatment demonstrated higher neuropsychological performance than those under haloperidol treatment. The performance was significantly higher on measures of learning and memory and executive and visuospatial functions. Particularly, the difference detected on Benton Judgment of Line Orientation Test was a new and rarely replicated finding. Due to some limitations of the study, our results are suggestive rather than conclusive. In spite of the limitations this study might suggest that in schizophrenic patients, the performance of clozapine treated patients in some domains of neurocognitive functions would be better than those of haloperidol treated patients. Future studies might focus on measures of visuospatial perception.