Effect of subjective sleep quality on learning and memory in drug-free patients with schizophrenia.

Objective: This study aims to elucidate the association paths between subjective sleep quality and the learning and memory ability of drug-free patients with schizophrenia.

Methods: 150 patients with schizophrenia were recruited. Information on clinical and socio-demographic was obtained, and a neurocognitive battery was administered. The Pittsburgh Sleep Quality Index (PSQI) was used to assess the quality of subjective sleep. The Verbal Learning Test and the Visual Learning Test that were taken from the MATRICS Consensus Cognitive Battery were used to assess the patient's ability to learn and recall. Structural equation modelling (SEM) was performed to examine the relationship between subjective sleep quality and learning and memory ability .The model was further modified and fitted.

Results: There were significant negative correlations between learning and memory variables and the PSQI scores or the PANSS scores. Significant direct effect of PSQI on Verbal Learning and Visual Learning, and significant indirect effect of PSQI on Verbal Learning and Visual Learning through psychotic symptoms were found in the most plausible SEM model that explains the data.

Conclusion: Subjective sleep quality has a direct impact on the ability to learn and memory, and indirectly affects the ability to learn and memory through psychotic symptoms in drug-free patients with schizophrenia. Sleep quality could be an intervention target for improving cognitive function in patients with schizophrenia.