I've read about thiamine megadosing a lot, it's not just for stutter, it can active some enzyme that otherwise wouldn't work, it help with energy production in brain which then can affect a tons of other stuff down the road. There are several forms of B1 and some works better for others or in other tissues/for other problems. TTFD is form of B1 that can be absorbed in brain easily. With megadosing B1 there is ofthen mention paradoxical reaction when for some days up to a month can make you feel bad, but then things gets better (it can be improved with magnesium and other minerals). There are lot of anecdotes and studies where B1 seems like magical stuff. I recommend everyone to check Eliot Overton, he has lot of videos, podcast and other stuff about B1 and how to megadose it safely.