According to Catherine Darley, N.D. of The Institute of Naturopathic Sleep Medicine, Inc., there is some research to show that by affecting the circadian rhythm, melatonin promotes more time in REM sleep, which is the sleep stage most associated with dreaming. As such, Darley tells mbg the body's natural stores of the hormone can create “a big change in our dream experience” by potentially evoking more vivid dreams.
That being said, the jury’s still out on whether or not taking a melatonin supplement gives you crazy dreams. According to Darley, there isn’t enough solid research to suggest that taking melatonin would lead someone to have more odd dreams than usual.
However, if you’re taking melatonin to get back on track after a period of suboptimal sleep, Medina tells mbg it is possible to have some weird dreams when you start sleeping more through the night. It’s also possible that someone taking melatonin would experience odd dreams because melatonin can lead to overactivation in different parts of the brain.
“There are melatonin receptors all over the brain in regions like the cortex, thalamus, substantia nigra, nucleus accumbens, amygdala, hippocampus, cerebellum, and your eyes,” Medina explains. “These are areas that are heavily involved in learning, memory, processing fearful events and threatening stimuli, stress relations, and cognitive executive function. So, when taking an amount of melatonin that is larger than what the body is used to, it is not surprising why these areas are overactive with the amount of melatonin that is available on the market.”
Indeed, recent research shows that over the last 20 years, taking more than 5 milligrams of melatonin per day (much higher than the typical recommended dosage of 0.5 milligrams, which is more closely aligned with human physiological levels of the hormone) has become more common in the U.S. This raises some safety concerns, as experts agree that taking high doses of any hormone—especially one that is as widespread as melatonin—can throw off your body's natural hormone production.