Temporarily.
Last Friday night I wanted to get to sleep early and minimize my REM, so I took 1.2g Phenibut + 600mg GABA. Strangely, I didn't fall asleep until about 4AM. I woke up at 9AM and felt almost completely refreshed... And I felt better than I had for a few months.
I didn't take anything to help me sleep that night. Sunday my brain fog was back.
Tuesday night I tried just the Phenibut at 1g. Wednesday I had, once again, a high degree of lucidity. Since I had an interview and midterm Thursday, I tried the same thing Wednesday night. Thursday I was feeling pretty positive, though more tired, with a little less concentration. Since I know tolerance develops fast for Phenibut, I didn't take any Thursday or Friday.... and both days did not go well.
How could Phenibut allow me to feel better on 4-5 hours of sleep than I have in maybe 2 months with consistent 8-9 hours of sleep? It just doesn't add up.