A substitute ??? for marijuana's "calming effect"

As I understand it, the active ingredient in Cannabis is THC. THC inhibits (slows down) neurons from firing, including excitatory neurons and inhibitory neurons. By slowing down the excitatory neurons (from over-firing) it produces a calming effect on the body. It also relieves (to a degree) the job of the inhibitory neurons so even though they are also inhibited, they are replaced by the THC. Now, a naturally occurring amino acid in the brain called GABA, is a major inhibitory neurotransmitter (slows down the activity of nerve cells) thus calming down the body against stress and anxiety. So, THC is calming down nerve cells and GABA is calming down nerve cells. For those who are feeling irritable, short tempered, etc. (in other words, going through THC withdrawal) wouldn't GABA (a food supplement) be a fine substitute?