I started when I was 18, 22 now. I never had any sort of formal training though, just got into it because of isolation. I guess you could say being in high school drumline helped with sense of rhythm greatly, but as far as melodic sensibility? There was next to none. lol
I was diagnosed with chronic migraines, and had to go get multiple MRIs over my junior year.
At that point, I had to stop going to regular high school and go into online high school because my grades were slipping rapidly.
So it basically created a situation where I was stuck in a town 30 miles away from any friends or any events that might have happened in what was my social life. Music became somewhat of an obsession, completely engulfing my life and making me learn a new skill I never thought I'd pick up.