Yes, there's so much more to this than we currently know. My grandson(22m) has ADHD and is on the spectrum. He's in engineering school nevertheless, but has had a minor stutter and mumbling thing. I stutter, my husband's mother stuttered sometime in her life, and my father stuttered early in his life so there is a genetic aspect to all this. I have bipolar 2 as do my brothers and nieces but no one else stutters. There is an amazing poster on this site. Find Little_Acanthaceae for science-based information on our disorder. 🙀❤️😺