Melatonin is an endogenous hormone that helps to maintain your circadian rhythm.

Melatonin is also made synthetically and available without a prescription as an over-the-counter (OTC) dietary supplement in the U.S.

Melatonin has several proposed mechanisms of action against COVID-19.

• Blocks inflammasomes
• Improves sleep habits, reduces anxiety and stimulates immune response
• Prevents fibrosis
• Immunomodulation
• Antioxidation
• Anti-inflammatory
• Ameliorative effects

https://www.tandfonline.com/doi/full/10.1080/08830185.2020.1756284

http://www.melatonin-research.net/index.php/MR/article/view/95

https://www.sciencedirect.com/science/article/pii/S0168170220310157

https://www.mdpi.com/2072-6643/12/9/2561

http://melatonin-research.net/index.php/MR/article/view/118

http://melatonin-research.net/index.php/MR/article/view/79

https://onlinelibrary.wiley.com/doi/abs/10.1002/rmv.2109

http://www.melatonin-research.net/index.php/MR/article/view/84

https://onlinelibrary.wiley.com/doi/abs/10.1111/jpi.12732

https://www.sciencedirect.com/science/article/pii/S0014299920304210

https://www.sciencedirect.com/science/article/pii/S1201971221007980

https://onlinelibrary.wiley.com/doi/10.1111/jpi.12772

https://www.dovepress.com/implications-for-systemic-approaches-to-covid-19-effect-sizes-of-remde-peer-reviewed-fulltext-article-JIR

https://onlinelibrary.wiley.com/doi/full/10.1002/jmv.27312

https://www.mdpi.com/2076-3921/10/7/1152/htm

https://jcsm.aasm.org/doi/10.5664/jcsm.9554

https://www.sciencedirect.com/science/article/pii/S0162013421001938

https://osf.io/xw3np/

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3878090