Dopamine is a neurotransmitter that affects a WIDE range of functions in the body including but not limited to reward/motivation, motor function, emotion, learning, addiction, body regulation (sleep, blood pressure, etc), and other cognitive functions. I don’t think there is a “safe” approach to investigate stuttering. You cannot investigate one aspect while ignoring the others. People do not exist in isolation. Genetics, psychology, emotions, neuroanatomy, life experiences, and many other things all play a role and need to be considered as to what extent they impact a person stuttering. It may not be a direct link but due to the widespread use of it in the and body, it is reasonable to say that it may have a role in. How big that role is, I can’t tell you exactly without studying more. While there is some ties to dopamine in a number of disorders, it is just one of many aspects that impact stuttering. I did answer some points about emotions and stuttering in another comment I left including therapies that target emotional responses in stuttering.