Regulatory T cells mediate insomnia-related psychotic symptoms and cognitive impairment in chronic schizophrenia patients

Insomnia occurs frequently in schizophrenia patients and is often accompanied with severe psychotic symptoms and cognition impairment. Moreover, chronic insomnia is associated with immune alterations. This study explored the correlations between insomnia and clinical manifestations of schizophrenia and analyzed mediation effects of regulatory T cells (Tregs) on these correlations. In a total of 655 chronic schizophrenia patients, 70 persons (10.69%) had an ISI (Insomnia Severity Index) score >7 and were referred to as Insomnia group. Compared to non-Insomnia group, Insomnia group presented more severe psychotic symptoms (assessed by PANSS) and cognitive impairment (assessed by RBANS). The total effect of ISI on PANSS/RBANS total score was not significant due to the mediation effects by Tregs, in which Tregs strongly mediated the effect of ISI on PANSS total score in negative direction but mediated the effect of ISI on RBANS total score in positive direction. Pearson Correlation Coefficient revealed negative correlations between Tregs and PANSS total score or disorganization subscale of PANSS. Positive correlations existed between Tregs and RBANS total score, between Tregs and the subscales of attention, delayed memory, or language of RBANS. These mediation effects of Tregs on insomnia-related psychotic symptoms and cognitive impairment in chronic schizophrenia patients point to a potential therapeutic strategy of modulating Tregs for the patients.