cause of your stutter?

cause of your stutter? do people here know the cause of their stutters for the most part? did you all have yours for all / most of your lives??? ive yet to get an mri to check for brain damage perhaps from a sport related concussion since ive been too depressed and self loathing, but assuming it comes back "clean" i have to assume my cause is psychological trauma. i got my stutter when i was 13\-14.