Bit off-topic, but melatonin taken at right doses appears to work very well. (commonly prescribed doses are 10-30x too much and likely cause tolerance). See the post https://slatestarcodex.com/2018/07/10/melatonin-much-more-th...
Why buy 1mg pill when you can buy 100mg pill?
There actually is a condition that calls for extremely high (100mg+ doses), but it is a very rare thing, no one should ever consider that much without instruction from a doctor. But you'll find it right next to the normal <=5mg doses without any explanation.