First, antidepressants don't increase GABA in the brain. The don't work on GABA, they work on other neurotransmitters, and they don't even increase those, they just alter how the body uses them, so Abilify and ssris, for example don't target GABA. Benzos do target GABA, but don't necessarily increase it, again, they alter the way the body uses it mostly. GABA supplements don't generally cross the blood/brain barrier, so they don't usually increase GABA either.