Major Depressive Disorder (MDD) affects approximately 5% of the global population and represents the second leading cause of disability worldwide. Despite the availability of pharmacological treatments, particularly antidepressants, their efficacy remains limited: nearly 50 to 60% of patients do not respond adequately after 8 weeks of treatment. One of the most common and persistent symptoms in MDD is insomnia, which affects about 85% of patients and frequently persists even after partial improvement of mood symptoms. Insomnia is not only a residual symptom but also a marker of poor prognosis and treatment resistance. Addressing sleep disturbances directly has been shown to enhance both symptomatic and functional remission in depression, making it a promising target for intervention.
In clinical practice, combination strategies are increasingly employed to improve therapeutic response, particularly in patients who are only partially responsive to antidepressant medication. Among these strategies, chronotherapeutic interventions, such as light therapy and prolonged-release melatonin, offer a compelling approach. These treatments have demonstrated rapid antidepressant effects, with some studies reporting clinical improvements as early as the first week of treatment. Additionally, both interventions are known to positively influence sleep quality and circadian rhythm regulation, which are often disrupted in depressive disorders.
Light therapy (LT), in particular, has shown efficacy comparable to that of antidepressants and works by synchronizing the sleep-wake cycle. When used in combination with antidepressants, LT has been associated with significantly greater reductions in depressive symptoms than antidepressants alone. Similarly, prolonged-release melatonin has been recommended in the management of insomnia comorbid with depression, further supporting the rationale for combining these chronotherapeutic agents.
This study is a multicenter, randomized, double-blind, placebo-controlled trial designed in a 2x2 factorial format. It aims to evaluate the efficacy of two chronotherapeutic interventions, active light therapy (10,000 lux) for 8 weeks and 2 mg prolonged-release melatonin for 8 weeks, administered alone or in combination, in improving depressive symptoms at 8 weeks. The trial will enroll adult patients diagnosed with moderate to severe MDD and comorbid insomnia. The primary objective is to assess the change in depressive symptom severity, measured by the Montgomery-Åsberg Depression Rating Scale (MADRS) score, from baseline to week 8.
All participants, regardless of group allocation, will receive standard antidepressant treatment and structured sleep hygiene counseling to ensure a consistent baseline of care. This approach reflects real-world practices and enhances the ecological validity of the trial. The study also incorporates objective and subjective measures of sleep and circadian rhythms to explore the broader impact of the interventions.
By evaluating the combined and individual effects of light therapy and melatonin alongside standard care, this study seeks to establish an innovative and comprehensive therapeutic model. The goal is to improve outcomes for individuals with MDD and insomnia, particularly the substantial proportion of patients, up to 40%, who do not achieve adequate response with antidepressants alone. This trial represents a significant step toward more personalized, effective, and integrated treatment strategies for depression.
