Your life = my life right now. I've never really had to study while I was going through an episode until this semester. And buddy I feel your pain. It is so hard to concentrate on those darn concepts when your mind has a million and one other things it would rather think about.
My suggestions/ what worked for me. Studying around other people preferably friends who are aware of what your are going through. That way when they see you semi-freaking out/ not doing something they can get you back on track. Or make flashcards and have a friend quiz you. I found that making it fun helped me to. For my french midterm I found an open white board and started writing stories about my friends in french it was more engaging than just staring at my textbook and actually was enjoyable (bonus!)
Another route I like is the reward system when I find something that I actually enjoy while depressed I reward myself with it after 15 minutes of successful studying (imgur is my reward just so ya know).
I also agree with what vossie42 said making a (realistic) schedule really helps! After you map out exactly what you want to study it makes it seem less overwhelming and impossible!
and my last suggestion as corny as it may be is yoga. It really helped me focus and center/ calm myself before a study sesh
Power through my friend and good luck!