Adolescence and early adulthood (collectively categorized as "young people") is a transitional period associated with a number of key physiological, social and psychological changes. Sleep difficulties, notable in this age group, may adversely affect physical and mental health. Of interest is the impact of the natural shift in young people towards a more evening-type sleep pattern (chronotype), whilst social constraints encourage early waking to fit with school/work timings. This leads to a misalignment in sleep timing between weekdays and weekends, known as social jetlag, which may contribute to emerging mental health difficulties seen during this age group. A systematic literature review was undertaken to investigate the association between social jetlag and mental health outcomes. Systematic searching of electronic databases (The Cochrane Library; PsycINFO; CINAHL; Scopus; and PubMed), grey literature and review of reference lists identified seven studies which assessed associations between social jetlag and mental health outcomes in young people. Quality appraisal was completed using the Appraisal Tool for Cross-Sectional Studies. Findings appeared equivocal; however significant associations were revealed with social jetlag associated with clinical depression and seasonal depression, in female participants and high latitude regions. Quality of included studies was moderate (10-13 criteria met). A lack of homogeneity between study methodologies precluded the conduct of a meta-analysis. The ambiguous results found may result from confounding factors including non-comparable methods of measuring social jetlag and mental health both in this age group and the selected studies. Future research should address a lack of homogeneity through the development of an interdisciplinary core outcome set, and agreement on a standardized measure and calculation for social jetlag.
