Association between delta waves during sleep and negative symptoms in schizophrenia. Pharmaco-eeg studies by using structurally different hypnotics

We examined the effects of benzodiazepine (BZD) hypnotics and zopiclone (ZPC), a nonbenzodiazepine hypnotic, on sleep and psychiatric symptoms in schizophrenia, as well as the clinical correlates of these variables. Seven male schizophrenic patients chronically taking neuroleptics together with BZD were studied. We replaced BZD with ZPC and performed polysomnography (PSG) and Brief Psychiatric Rating Scale (BRPS) scoring before and after an 8-week ZPC treatment. The replacement of BZD with ZPC increased the mean amplitude of high-amplitude low-frequency delta waves on the frontal derivation recognized by period-amplitude analysis, and it decreased the BPRS negative-symptom score. Under the BZD treatment, the negative-symptom score correlated inversely with the mean amplitude of high-amplitude low-frequency delta waves. This correlation was weak and not significant under the ZPC treatment. Therefore, delta waves during sleep have a close correlation to negative symptoms in schizophrenia, and such a correlation could be influenced by hypnotics. Although these are preliminary findings, it was suggested that, compared with BZD, ZPC might be a beneficial hypnotic in regard to both sleep and negative symptoms of chronic schizophrenic patients.