i mean there's really almost no research in the literature on possible biomedical causes of stuttering but as far as I know it statistically clusters with other neurological issues like tics, tourettes, autism etc. There are a few papers on the association between the MTHFR gene and autism, one claiming 98% of autism cases presented with the gene mutation. https://documentinghope.com/mthfr-mutation/ I've found AI like chatgpt or grok to be super helpful in my research but unfortunately if the studies haven't been done, all AI can do is speculate.