Evidence supporting the use of: Melatonin
For the health condition: Seasonal Affective Disorder

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Synopsis

Source of validity: Scientific
Rating (out of 5): 3

Melatonin is a hormone naturally produced by the pineal gland that regulates circadian rhythms, including the sleep-wake cycle. Its use in treating Seasonal Affective Disorder (SAD) is supported by scientific evidence, though the strength of this evidence is moderate rather than robust. SAD is a form of depression that typically occurs during the winter months when daylight hours are shorter. The underlying pathophysiology of SAD appears to involve disruptions in circadian rhythms and melatonin secretion in response to changes in light exposure.

Several clinical studies have examined the use of melatonin in SAD. A key hypothesis is that people with SAD have a delayed circadian rhythm, and timed administration of melatonin can help realign their internal clock with the external environment. A 2006 randomized controlled trial published in Proceedings of the National Academy of Sciences demonstrated that low-dose, afternoon/evening melatonin helped correct circadian misalignment and improved depressive symptoms in SAD patients. Meta-analyses and systematic reviews suggest a potential benefit, but results are mixed, and melatonin is not universally effective for all individuals with SAD. Light therapy remains the first-line treatment.

In summary, there is scientific rationale and moderate-quality evidence to support the use of melatonin in treating SAD, particularly for patients with circadian phase delay. However, further large-scale, well-controlled studies are needed to clarify optimal dosing, timing, and patient selection.

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