This has been posted & discussed extensively in the past

https://news.ycombinator.com/item?id=45867371

As I understand it, tryptophan can become either niacin or serotonin in metabolism.

Serotonin is the natural source of all malatonin.

Niacin and tryptophan will maximize the serotonin pathway, but this is deadly with an SSRI.

Friendly reminder that the maximum dose for melatonin, if it is to be used at all, should be limited to 0.3mg (300 mcg), many formulations are massively over-dosed

My experience, is that melatonin is a realy fucked up drug it will strip your psyche and feed it back to you in one epic motherfucker of a dream but then seems to loose that quickly and not realy do anything at all, and is totaly pointless. Plus the harder I work physicaly, the better I sleep, eat, think, plan, strategise, and reafirm my capacity to deal with stuff. For people who dont do physical work, like my father, leading a very,very, disaplined orderly life, with lots of self care,and even when when things go wrong maintaining routine and habits, seems to be key.