There is currently no compelling evidence that a combination of melatonin and cannabidiol (CBD) improves sleep beyond what can be explained by melatonin alone.
Melatonin and CBD is a popular supplement combo for improving sleep, based on supposedly complementary mechanisms of action (i.e., melatonin promoting sleep onset and CBD theoretically reducing sleep disruption). However, there is little evidence that CBD can improve sleep quality on its own.[1] But what about when combined with melatonin?
One 4-week randomized controlled trial examined the effect of melatonin and several cannabinoids (including CBD), alone or in combination, on sleep in 1,784 people with sleep disturbances.[2] Ultimately, taking a combination of CBD, cannabinol (CBN), and melatonin did not clearly reduce sleep disturbances compared to taking melatonin alone. Unfortunately, the lack of placebo group and the inclusion of other cannabinoids (e.g., CBN) limits the generalizability of this study.
It’s possible that taking CBD could increase melatonin levels by inhibiting the enzyme CYP1A2,[3] which metabolizes melatonin.[4] In theory, this could mean CBD would make melatonin supplements more potent. However, this has not yet been directly confirmed in humans.