Several prescription patterns of antipsychotic drugs influence cognitive functions in Japanese chronic schizophrenia patients

OBJECTIVE: We hypothesized that an excessive dose of antipsychotic drug and/or a larger number of antipsychotic drug worsens cognitive functions in schizophrenia patients. To confirm the hypothesis, we compared several cognitive functions in the patients taking a second-generation antipsychotic drug (SGA) only (SGA monotherapy group) with those in patients taking more than two kinds of antipsychotic drugs (polypharmacy group). METHODS: The cognitive functions of 136 chronic schizophrenia patients were evaluated using the Brief Assessment of Cognition in Schizophrenia, Japanese-language version (BACS-J). RESULTS: A significantly negative correlation was found between the composite score in the BACS-J and the chlorpromazine equivalence of doses of antipsychotic drugs in whole patients (r = -0.43, P < 0.001). Schizophrenia patients in the polypharmacy group had lower composite scores than those in the SGA monotherapy group in the BACS-J. No difference was observed in the composite score and the primary score in each item in the BACS-J between patients with first- plus second-generation antipsychotic drug (FGA + SGA group) and those with two kinds of SGA (SGA + SGA group). CONCLUSION: These results suggest that an excessive dose of antipsychotic drugs regardless of FGA and SGA might cause the deterioration of cognitive functions in chronic Japanese schizophrenia patients.