Melatonin is a good natural sleeping supplement that many with sleeping problems find useful, but being a hormone, you always need to use it with caution. Ever since it was categorized as a dietary supplement in the early 90s and allowed to be sold over the counter, melatonin has never been reported to produce any serious side effects.
Obviously, nearly twenty years of widespread usage is quite long to validate that it’s fairly safe, but all the same, it should never be taken in large doses for a prolonged period. Certain people may react adversely to it more than others. So far, most studies have found melatonin in low dosages to be safe, for at least for up to 3 months of continuous use.
If you are depressed or undergoing psychological/emotional problems, melatonin may make them worse, especially if you take it at high doses. It can cause a heavy feeling of mental dullness throughout the day, even if it doesn’t translate into sleep for you. Melatonin may help with some types of insomnia, but unfortunately not all types.
This mental fog during daytime may have to do with the effect of the supplemental melatonin affecting physiology outside of the melatonin phase response curve (PRC). Phase response curve is the shifting of phases in a circadian rhythm affected by a stimulus or catalyst (melatonin here).
Therefore, remember to only take melatonin just before bedtime at night, and even if you still cannot sleep for hours, do not take additional doses nearer to the morning, or you could end up feeling pretty gray, the next day.
Aside from mental fog, other side effects like drowsiness, slow heartbeat, nausea, and headaches have been reported. Besides that, excess melatonin can cause nightmares during sleeping. Here is some of my advice on melatonin dosage.
Those who should not be taking melatonin include:
- Depressed people/people with mental illness
- Pregnant women/women trying to conceive
- People with cancer
- People on steroids
- People with severe allergies
- People with leukemia/lymphoma
Aside from the side effects, a drawback of prolonged excess melatonin supplementation is the possibility of depressing your own pineal gland’s production and reducing its ability to secrete melatonin on its own. That is why it is best to periodically go off your melatonin supplements even if you never overdose on it. Also remember, if stopping melatonin after long term use, it is best to taper off the dosage to avoid with rebound insomnia.