I've never had much success with just l-theanine and ashwaganda alone but I think the GABA neurotransmitter is the key neurotransmitter in the speech center of the brain. I've found this to be a miracle stack for curing stuttering l-theanine 500mg l-arginine 750mg Taurine 1500mg Magnesium gyyclenate 3 in 1 - 384mg CBG - vape a little In addition I also find putting 0.25mg of a nicotine lozenge under the tongue helps (but only when taken with the other GABA enhancing stuff) I also find vaping terpenes and CBD help stuttering through different neuropathways to the GABA. In addition I take NAC NR Creatine Don't think these three have much effect on stuttering tho - but they do make you feel great.