https://sites.google.com/view/lunavelle-sleep-patches-usa/

Melatonin is a hormone your brain makes in response to darkness. It signals your body that it's time to wind down. That's it. It's a signal, not a sedative.
When you take it as a supplement, you're adding an external hormone on top of what your body already produces. Do that consistently, and your body's own melatonin production can decrease. You end up needing more of the supplement just to get the same effect.