Association of sleep duration and risk of mental disorder: a systematic review and meta-analysis

Background The effects of sleep duration on the development of mental illness remain controversial. Therefore, it is necessary to identify the effects of long or short sleep duration on psychological disorders, which could reveal new ways for preventing and treating mental health conditions cheaply.Methods Identifying published papers was accomplished by using the following five English databases on March 16, 2022: PubMed, MEDLINE, Embase, Web of Science databases, and Scopus. Cross-sectional and cohort studies were considered if they evaluated the association of sleep duration with all kinds of mental illness in adults. We excluded case reports, editorials, narrative reviews, and studies without detailed information on sleep duration. Summary effect-size estimates were expressed as risk ratios (RRs) or odds ratios (ORs) with 95% confidence intervals and were evaluated using random-effect models. Mantel-Haenszel's random-effects model was used to estimate the inconsistency index (I2) and Tau2 index (measurement of heterogeneity).Results A total of 52 studies were included in this analysis, consisting of 14 cohort studies and 38 cross-sectional studies. These studies involved a combined sample size of 1,407,891 participants who met the inclusion criteria. Cohort (adjusted RR = 1.42, 95% CI: 1.26-1.60, P < .001, I-2 = 37.6%, Tau(2) = 0.014) and cross-sectional studies (adjusted OR = 1.67, 95% CI: 1.57-1.77, P < .001, I-2 = 79.7%, Tau(2) = 0.060) concluded that short sleep duration increased mental disorder risks. The same conclusions were acquired in the subgroup analysis, especially for depression (adjusted RR = 1.43, 95% CI: 1.24-1.65, P < .001, I-2 = 80.4%, Tau(2) = 0.082), anxiety (adjusted RR = 1.30, 95% CI: 1.04-1.63, P = .002, I2 = 0.0%, Tau(2) = 0.000), and PTSD (adjusted RR = 1.35, 95% CI: 1.04-1.76, P = .022, I-2 = 24.1%, Tau(2) = 0.013) in cohort studies. The results of subgroup analysis indicated that long sleep duration was not a risk factor for depression (adjusted RR = 1.15, 95% CI: 0.98-1.34, P = .088, I-2 = 63.4%, Tau(2) = 0.045) and anxiety (adjusted RR = 1.37, 95% CI: 0.93-2.03, P = .114, I-2 = 0.0%, Tau(2) = 0.000).Conclusions Short sleep duration, not long sleep duration, is an independent predictor of developing mental disorders, particularly anxiety and depression.