I don't recall cigarettes having any effect on my stutter. Cannabis used to be fun and talking felt fluent and natural when just saying inconsequential nonsense, but when trying to function normally it increased my anxiety and made my stutter worse. The times I've used LSD I've been so chilled out and haven't stuttered (as far as I remember), but haven't tried it while functioning in the normal world. Microdosing psilocybin has been nice while going about my day. Accidental large doses definitely caused problems in the world. Private large therapeutic doses with therapeutic and meditative techniques to deal with the emotions that come up have been the absolute best thing for my mental health and my stutter as it helps to process the emotional causes of these problems. I'm not sure there's any help for the neurological causes though, but I'd love it if there was. I've done changa (which contains DMT) a few times and it's like a strong psilocybin trip but in 5 minutes instead of 6 hours.