I also didn't really start drinking until I was in my late 20s. Before that like when I first left home at 18, I smoked weed but only cos people around me were doing it , & I wasn't at all dependent on it. Drinking at home, alone, was the start of problem drinking. I think, it was when multiple problems & responsibilities in my life were piling up - like studying for a full time degree with no support whilst working part-time plus being a single parent plus my son being on the autistic spectrum (which I didn't realize at the time).. Always had hardship & problems in my life really but it's when you have lots of them all at once and more responsibilities building up.