Insomnia is a common feature in schizophrenia, and is characterized by an increase of sleep latency (SL), as well as reductions in total sleep time (TST) and sleep efficiency (SE). Regarding sleep architecture, non rapid -eye-movement (NREM) sleep, slow wave sleep (SWS) and rapid-eye-movement (REM) sleep latency are decreased, whereas REM sleep tends to remain unchanged. According to polysomnographic studies, clozapine, olanzapine, quetiapine and ziprasidone administration increased TST and/or SE in healthy subjects. Additionally, olanzapine and ziprasidone augmented SWS, while changes corresponding to REM sleep were inconsistent. Furthermore, administration of clozapine, olanzapine and paliperidone to patients with schizophrenia was followed in most instances by a significant reduction of SL and an increase of TST and SE. In addition, olanzapine and paliperidone augmented SWS and REM sleep. By contrast, quetiapine administration further disrupted sleep as judged by the increase of SL, wake time after sleep onset (WASO) and REM sleep latency, and the reduction of SWS and REM sleep. No consistent effects on sleep variables were obtained during treatment with risperidone. To date, no polysomnographic studies have been published on the effects of aripiprazole, asenapine, iloperidone and lurasidone on sleep in either healthy subjects or patients with schizophrenia. Taken together, this evidence supports the conclusion that second generation antipsychotics (SGAs) including clozapine, olanzapine and paliperidone may ameliorate insomnia in patients with schizophrenia. (C) 2016 Elsevier Ltd. All rights reserved.