Serotonin and feeling spaced out

Just tried out a green tea extract for the first time in about a year. What I noticed was that I got the same exact spaced out numb feeling I had when taking 5-htp. It was exactly what feeling "spaced out" is and it seems like this may be an interaction with serotonin in my brain. I would also like to mention that others on SSRIs have reported similar effects.

Could anyone explain to me what EGCG, through green tea extract could be doing through inhibiting dopa decarboxylase and thus increasing serotonin? I didn't think I would feel zoned out similar to what others on SSRIs have. I just want to know whether this is detrimental or not since Green tea polyphenols are known to have neurogenic effects.