The present meta-analysis investigated the characteristics of sleep in patients with schizophrenia without neuroleptic treatment at the time of sleep recording. The 20 selected studies included 652 participants (321 patients with schizophrenia and 331 healthy subjects). Effect sizes were evaluated using d values for the following sleep variables: sleep latency (SL), total sleep time (TST), sleep efficiency index (SEI), total awake time (TAT), stage 2 percentage (S2%), stage 4 percentage, slow-wave-sleep percentage, rapid-eye-movement (REM) percentage, and REM latency. The initial meta-analysis revealed that patients with schizophrenia have the following sleep disorders: increased SL, decreased TST, and decreased SEI. A moderator analysis revealed that these sleep disorders were worse for the neuroleptic-withdrawal group relative to the never-treated group. However, only never-treated patients showed significantly increased TAT and diminished S2%. These results confirm that patients with schizophrenia have sleep disorders that are not necessarily a consequence of neuroleptic treatments, suggesting that sleep disorders are an intrinsic feature of schizophrenia. However, it must be noted that some sleep disorders may be amplified by residual effects of neuroleptic withdrawal, while others appear to be dampened by neuroleptic treatment.

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