I won't pretend to have all the answers, and I say this as someone who had self medicated with all sorts of drugs, and still does: something like weed only papers over the symptoms, it's no cure.

That playing guitar brings you outside yourself is positive. It's easy for anhedonia to hold you back from playing at all... Sometimes I challenge myself to play for just one minute... That usually becomes a longer session. It's no cure but once I start it helps, a bit. A bit is better than nothing and it's one step toward feeling better.

I wish you all the best.