Try Googling the topic - there is plenty of information about this online. But most importantly, for the person considering it, discuss the issue with your doctor as it is not a trivial matter to stop taking antidepressants.
On this forum, you will find plenty of information about melatonin, 5-HTP and GABA. However, it is dangerous to mix psychiatric medication with those supplements - especially, 5-HTP.
They can form a part of the withdrawal plan but must be coordinated with the help from your medical practitioner.
Also, do keep in mind that some people should just stay on antidepressants, OK. Sometimes, it is the only thing that keeps their mind semi-functional. Better that than becoming a homeless raving lunatic roaming the streets.
FWIW.