I think the forgetting aspect is actually the reason why cannabis is so good for PTSD. With PTSD you have memories that are so burned into your brain that those pathways keep activating, and I think that THC softens those connections.
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I think it can help soften the blow from childhood abuse memories too. If the Feds would just legalize it the universities and government national laboratories could begin meaningful research into specific parts of the chemical entourage marijuana is. I think there is huge potential.