I've been taking B1 along with magnesium for a couple of years now, roughly following the thiamine protocol. I think it has some positive effect on my speech and general anxiety. I couldn't say how much of that is placebo and how much is due to the extra vitamins and minerals (I take others as well) but I take them habitually and barely even think about why. I do a lot in terms of nutrition to minimise anxiety - barely any refined sugar, as little ultra-processed food as possible, and it all helps. I wouldn't rely on one strategy though, but if it's beneficial it's worth doing.