Psychogenic vs. Neurogenic stuttering. How to tell the difference, and test for one, or the other

Psychogenic vs. Neurogenic stuttering. How to tell the difference, and test for one, or the other I’ve stuttered since I was 28. No history prior. I never figured out if my stuttering was from a brain injury, or mental health problems. How can I test to figure this out? I want a definitive answer so I can find the best treatment plan for myself