Side Effect 5: Headache and Irritability
People who consume high doses of this supplement or people who are are extremely sensitive to melatonin are the ones who develop headaches when using melatonin. Melatonin affects the serotonin levels in the brain, which when interfered with, may induce headaches.
Irritability is a feeling of agitation and annoyance. People who take high dose of melatonin or are sensitive to it are more likely to feel irritable on a daily basis.