Effects of risperidone and quetiapine on cognition in patients with schizophrenia and predominantly negative symptoms

Evidence suggests that neurocognitive impairment is a key factor in the pathology of schizophrenia and is linked with the negative symptoms of the disease. In this study the effects of the atypical antipsychotics quetiapine and risperidone on cognitive function in patients with schizophrenia and with predominantly negative symptoms were compared. Patients were randomly assigned to double-blind treatment with quetiapine or risperidone for 12 weeks. Cognitive function was assessed at baseline, Week 6 and Week 12. Efficacy was assessed using the Positive and Negative Syndrome Scale (PANSS) and the Scale for the Assessment of Negative Symptoms (SANS) at baseline, Week 6 and Week 12. Extrapyramidal side-effects were assessed each week using the Simpson-Angus Scale (SAS), adverse events were recorded as additional indicators of tolerability throughout the trial. In total, 44 patients were enrolled in the study. Data from the 34 patients who completed cognitive assessments at two or more time points out of three (baseline, Week 6 and Week 12) are analysed here. Quetiapine improved significantly global cognitive index z-scores at both Week 6 (p < 0.001 vs. baseline) and Week 12 (p < 0.01 vs. baseline), whereas risperidone improved significantly global cognitive index z-scores at Week 12 (p < 0.05). Between-group comparisons at Week 6 showed significantly greater improvements in working memory and verbal memory with quetiapine than risperidone (p < 0.05) and a significantly greater improvement in reaction quality/attention with quetiapine than risperidone at Week 12 (p<0.05). Quetiapine and risperidone produced significant improvements from baseline in PANSS total (p<0.001) and subscale scores at Week 12. Significant improvements in SANS total score were also seen in both the quetiapine (p < 0.001) and risperidone (p < 0.01) groups at Week 12 compared with baseline. SAS scores, measuring the incidence of extrapyramidal side-effects, were higher in patients receiving risperidone compared with those receiving quetiapine, and significant differences were seen at Weeks 3, 4, 5 and 7. Both quetiapine and risperidone improved cognition according to changes in cognitive index scores from baseline to Week 12. These results suggest that quetiapine and risperidone provide valuable treatment options for patients with schizophrenia with predominantly negative symptoms. Also, the improvements in cognition following treatment with quetiapine and risperidone may enhance long-term outcomes for these patients.