The researchers compiled the results of five separate studies on melatonin and hair loss. One of the studies - which involved 30 men and women - showed a significant reduction in the severity of androgenetic alopecia after taking melatonin for 30 and 90 days. Another study involving 60 men and women who suffered from hair loss found a significant reduction in hair loss in the female participants, with less effect on the men. In another study, researchers concluded that a melatonin solution applied to the scalps of 40 women with hair loss significantly increased hair growth compared to participants who received a placebo.
While it is unclear exactly how melatonin promotes hair growth, some experts suggest it may have to do with the same circadian rhythms that control the sleep-wake cycle. The hair growth cycle in humans is also under circadian control, which could explain the connection.
The review authors wrote, "Because safety and tolerability were good in all studies, topical application of a cosmetic melatonin solution may be considered as a treatment option for androgenetic alopecia."