Evidence supporting the use of: 5-Hydroxytryptophan (5-HTP)
For the health condition: Seasonal Affective Disorder

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

5-HTP (5-hydroxytryptophan) is a naturally occurring amino acid and chemical precursor in the biosynthesis of serotonin, a neurotransmitter that plays a significant role in mood regulation. The rationale for using 5-HTP to support or treat Seasonal Affective Disorder (SAD) is grounded in the "serotonin hypothesis," which suggests that lower serotonin levels contribute to depressive symptoms seen in SAD, particularly during the winter months when sunlight exposure is reduced. Several small clinical trials and open-label studies have investigated the use of 5-HTP for various forms of depression, including SAD. Some evidence suggests that increasing serotonin synthesis via 5-HTP supplementation may help alleviate depressive symptoms, and a few early studies (e.g., Lôo et al., 1985) have reported improvements in SAD patients. However, these studies are often limited by small sample sizes, lack of placebo controls, or methodological flaws. While the biological plausibility is strong, high-quality, large-scale randomized controlled trials specifically assessing 5-HTP for SAD are lacking. As a result, while the use of 5-HTP for SAD is supported by a scientific rationale and limited preliminary evidence, its efficacy is not well-established, and it is not considered a first-line treatment. Light therapy and antidepressant medications have much stronger evidence bases. Caution is also advised due to potential side effects and drug interactions.

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