Background: Sleep disturbances are highly prevalent in depressive disorders and are increasingly recognized as both core symptoms and risk factors. Insomnia, hypersomnia, fragmented sleep, and circadian rhythm disruptions—including social jetlag—contribute to the onset, severity, and persistence of depressive symptoms, while impairing cognitive, emotional, and psychosocial functioning. Methods: A narrative literature review was conducted using PubMed, Web of Science, and Scopus, focusing on peer-reviewed studies published between 2000 and 2025. Studies examining subjective and objective measures of sleep in adult populations with depressive disorders were included, with emphasis on clinical presentation, functional outcomes, and treatment response. Results: Sleep disturbances are associated with greater depressive symptom severity, earlier onset of illness, impaired psychosocial functioning, and poorer response to treatment. Insomnia is the most common disturbance, while circadian misalignment, including social jetlag, is particularly relevant in adolescents, shift workers, and evening chronotypes. Mechanistic evidence links sleep disturbances to mood dysregulation through HPA axis disruption, inflammation, and altered melatonin secretion. Sleep-focused interventions, such as cognitive-behavioral therapy for insomnia, structured sleep schedules, and light therapy, improve both sleep quality and depressive outcomes, and enhance responsiveness to pharmacological treatments. Conclusion: Sleep disturbances are integral to the clinical and psychosocial presentation of depression. Early identification and targeted management of insomnia, hypersomnia, and circadian misalignment should be incorporated into routine care to optimize symptom control, functional outcomes, and long-term prognosis.
Susek et al. (Fri,) studied this question.