• Qiu-Qiang Zheng, Wei-Wei Yang, Shan-Shu He, and Yi-Ran Li.
• School of Education Science, Huizhou University, 46, Yanda Road, Huizhou, Guangdong Province, 516007, P.R. China.
• Postgrad Med J. 2025 Feb 5.

ObjectivesThis study aimed to explore the causal association between sleep duration and depression in adolescents and young adults.MethodsWe conducted a systematic review and Mendelian randomization (MR) to research the causal relationship between short sleep duration and adolescent depression risk from an observational and genetic perspective. In the systematic review, we searched observational studies from the PubMed, Embase, and Cochrane Library databases. In the MR analysis part, we screened Single Nucleotide Polymorphism (SNP) significantly relative to short sleep and conforming MR concept to investigate the genetic causality.ResultsAll research evidence shows that adolescents who sleep <6 h have the highest rates of depression. According to the MR result, short sleep duration significantly affected the depression risk (odds ratio, 1.034; 95% confidence interval, 1.012-1.058, P = .003). Sleep duration of 7-8 h has the lowest depression incidence. Insufficient sleep (≤6 h) and excessive sleep (≥8 h) also elevates adolescent depression risk. Genetic evidence shows that short sleep duration (<6 h) has significant causal effects on depression risk.ConclusionsSleep duration was causally associated with depression in adolescents and young adults. Sleep duration of <6 h or >8 h daily increases the depression risk in adolescents and young adults.© The Author(s) 2025. Published by Oxford University Press on behalf of Fellowship of Postgraduate Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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