Systematic review and meta-analysis of the relationship between sleep disorders and suicidal behaviour in patients with depression

BACKGROUND: The potential link between sleep disorders and suicidal behaviour has been the subject of several reviews. We performed this meta-analysis to estimate the overall association between sleep disorders and suicidal behaviour and to identify a more specific relationship in patients with depression. METHODS: A systematic search strategy was developed across the electronic databases PubMed, EMBASE and the Cochrane Library from inception to January 1, 2019 for studies that reported a relationship between sleep disorders and suicidal behaviour in depressed patients. The odds ratio (OR) and corresponding 95% confidence interval (CI) were used to measure the outcomes. Heterogeneity was evaluated by Cochran’s Q test and the I(2) statistic. The Newcastle-Ottawa Scale (NOS) was adopted to evaluate the methodological quality of each of the included studies, and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess the quality of the evidence. We calculated the overall association between sleep disorders and suicidal behaviour and estimated more specific categories, including insomnia, nightmares, hypersomnia, suicidal ideation, suicide attempt, and completed suicide. RESULTS: A total of 18 studies were included in this study. Overall, sleep disorders were closely related to suicidal behaviour in patients with depression (OR = 2.45 95% CI: 1.33 4.52). The relatively increased risks of sleep disorders with suicidal ideation, suicide attempt and completed suicide ranged from 1.24 (95% CI: 1.00 1.53) to 2.41 (95% CI: 1.45 4.02). Nightmares were found to be highly correlated with the risk of suicidal behaviour (OR = 4.47 95% CI: 2.00 9.97), followed by insomnia (OR = 2.29 95% CI: 1.69 3.10). The certainty of the evidence was rated as very low for the overall outcome and the major depression subgroup and was rated as low for the depression subgroup. CONCLUSIONS: This meta-analysis supports the finding that sleep disorders, particularly nightmares and insomnia, increase the risk of suicidal behaviour in depressed patients. Considering that all included studies were observational, the quality of the evidence is rated as very low. More well-designed studies are needed to confirm our findings and to better explain the mechanisms by which sleep disorders aggravate suicidal behaviour in depressed patients.