Objective: The effect of antipsychotic drugs on quantitative electroencephalography (EEG) has been mainly examined by the administration of a single test dose or among patients using combinations of other psychotropic drugs. We therefore investigated the effects of strict monotherapy with antipsychotic drugs on quantitative EEG among schizophrenia patients. Methods: Data from 2,364 medical reports with EEG results from psychiatric patients admitted to the Hokkaido University Hospital were used. We extracted EEG records of patients who were diagnosed with schizophrenia spectrum disorders and who were either undergoing strict antipsychotic monotherapy or were completely free of psychotropic drugs. The spectral power was compared between drug-free patients and patients using antipsychotic drugs. We also performed multiple regression analysis to evaluate the relationship between spectral power and the chlorpromazine equivalent daily dose of antipsychotics in all the patients. Results: We included 31 monotherapy and 20 drug-free patients. Compared with drug-free patients, patients receiving antipsychotic drugs demonstrated significant increases in theta, alpha and beta power. When patients taking different types of antipsychotics were compared with drug-free patients, we found no significant change in any spectrum power for the aripiprazole or blonanserin groups. Patients taking risperidone demonstrated significant increases in alpha and beta power. Patients taking clozapine and olanzapine demonstrated significant slow wave increases. Multiple regression analysis revealed that the chlorpromazine equivalent dose was positively associated with theta power. Conclusion Use of any antipsychotic drug by patients was associated with a dose-dependent increase in theta power. However, each type of antipsychotic demonstrated different spectral power changes.

Objective: The effect of antipsychotic drugs on quantitative electroencephalography (EEG) has been mainly examined by the administration of a single test dose or among patients using combinations of other psychotropic drugs. We therefore investigated the effects of strict monotherapy with antipsychotic drugs on quantitative EEG among schizophrenia patients. Methods: Data from 2,364 medical reports with EEG results from psychiatric patients admitted to the Hokkaido University Hospital were used. We extracted EEG records of patients who were diagnosed with schizophrenia spectrum disorders and who were either undergoing strict antipsychotic monotherapy or were completely free of psychotropic drugs. The spectral power was compared between drug-free patients and patients using antipsychotic drugs. We also performed multiple regression analysis to evaluate the relationship between spectral power and the chlorpromazine equivalent daily dose of antipsychotics in all the patients. Results: We included 31 monotherapy and 20 drug-free patients. Compared with drug-free patients, patients receiving antipsychotic drugs demonstrated significant increases in theta, alpha and beta power. When patients taking different types of antipsychotics were compared with drug-free patients, we found no significant change in any spectrum power for the aripiprazole or blonanserin groups. Patients taking risperidone demonstrated significant increases in alpha and beta power. Patients taking clozapine and olanzapine demonstrated significant slow wave increases. Multiple regression analysis revealed that the chlorpromazine equivalent dose was positively associated with theta power. Conclusion Use of any antipsychotic drug by patients was associated with a dose-dependent increase in theta power. However, each type of antipsychotic demonstrated different spectral power changes.