Correlation between Sleep and Cortisol levels in Adolescents - A Systematic Review

Background: Sleep and cortisol are closely intertwined through the hypothalamic–pituitary–adrenal (HPA) axis, with dysregulation contributing to stress, impaired cognition, and emotional disturbances. Adolescence is a critical period marked by hormonal and developmental changes that may alter this relationship. Methods: Following PRISMA guidelines, a systematic search was conducted across PubMed, Scopus, and Google Scholar for studies published between 1974 and 2024. Eligible studies included adolescents aged 10–19 years, assessing sleep parameters and cortisol levels. Out of 387 studies screened, 13 met the inclusion criteria. Risk of bias was evaluated using the Cochrane RoB-2 tool, and findings were synthesized narratively. Results: The review included 13 studies with a mean participant age of 15.7 years. Sleep duration declined with age, averaging 7.5 ± 1.2 hours, with chronic restriction (≤6 hours) linked to elevated cortisol (+23.4%, p = 0.003) and impaired cognition (−15%, p = 0.005). Females exhibited greater sleep disturbances and a stronger cortisol awakening response, while males showed shorter sleep and higher evening cortisol levels. Pubertal stage influenced both sleep and cortisol, with late-pubertal adolescents showing fragmented sleep and blunted morning cortisol responses. Poor sleep efficiency (<80%) correlated with higher evening cortisol and reduced attention. REM sleep was positively associated with emotional regulation and negatively with evening cortisol. Conclusion: This review highlights a strong bidirectional relationship between sleep quality and cortisol regulation in adolescents, with significant effects of age, gender, and pubertal stage. Poor sleep exacerbates HPA axis dysregulation, increasing vulnerability to stress, cognitive deficits, and emotional instability. Promoting healthy sleep habits during adolescence may mitigate stress-related risks and improve long-term well-being.