It might have come from India or from surrounding areas in the Mediterranean, and crossed over into the Mystery Religions, with their initiation rites and psychedelic potions. I got the reference from some books by the comparative mythologist Algis Uzdavinys.

Here are some other links (one is an MA thesis, but it seems pretty thorough):

https://en.wikipedia.org/wiki/Iatromantis

https://dionysianartist.wordpress.com/2017/01/23/the-cults-of-dionysos-ecstatic-practices-and-shamanism-in-classical-greece/

https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=kent1512462129881859&disposition=inline