The relationship between sleep and suicidality in schizophrenia spectrum and other psychotic disorders: A systematic review

Individuals with Schizophrenia Spectrum Disorders (SSDs) have significantly higher rates of suicidal thoughts, attempts, and death by suicide in comparison to the general population. Sleep disturbances (reduced duration, timing and quality of sleep) are risk factors for suicidality in the general population, with research indicating the relationship is both immediate and accumulative. Sleep disturbances are also considered to be implicated in the onset and exacerbation of psychotic symptoms in SSDs. Reducing the risk of suicidality in SSDs remains an important public health priority, thus exploration of contributing risk factors is warranted. Sleep monitoring may also offer an adjunct risk monitoring method to suicidality assessments in SSDs, and a potential treatment target for psychotic symptoms. This review aimed to explore proximal and longitudinal relationships between selfreported and objectively measured sleep and suicidality in SSDs and other psychotic disorders. A comprehensive search of four databases was conducted. Eleven studies met the inclusion criteria (10 cross sectional and 1 longitudinal). Narrative synthesis indicated that self-reported sleep disturbances and sleep disorders (e.g. insomnia) were associated with increased risk of suicidal ideation and attempt. However, one study employing polysomnography did not find sleep to be associated with suicidality. Methodological limitations of the evidence base include: i) little experimental or longitudinal evidence, (ii) self-report and/or single item assessment of sleep disturbance, (iii) limited use of validated measures of suicidality, (iv) considerable research in long-term schizophrenia but sparse evidence in early psychosis. Future research should explore (i) cross-sectional and longitudinal relationships between specific aspects of suicidality and objective sleep parameters, (ii) use qualitative or mixed-methods designs to disentangle the nuances and bidirectionality in the sleep-suicide relationship, (iii) explore the psychological processes underpinning or mediating the sleep-suicide relationship in SSDs.