I haven't tried straight GABA; my understanding (a few years ago, though! so dated info) was that it didn't absorb very well. But I had great success for anxiety with L-theanine for a while. Trouble was, they didn't make a slow-release capsule and I'd crash hard if I didn't take it perfectly.

Tangentially, the only thing I remember is that while taking a isolate like GABA or theanine to ensure that it is isolated and not a green tea concentrate-- cos the latter can contain huuuge amounts of xanthines (caffeine, theobromine, theophylline.)

Good luck! Hope it works out awesomely for you!