My depression activated partway into puberty, and it was Bad^(TM) until I started herbal self-medication when I got to buy my own stuff, and even then it was pretty lousy until I got on actual psych meds. Before puberty, it was mostly just that I was surrounded by assholes and had no friends to speak of.

I am greatly in favor of kids getting access to trustworthy adults who are trained to assess these things.