The problem with being mentally is that it’s, quite literally, all in your mind. The other problem, is that having an illness which happens to affect one particular organ means you don’t seem to qualify as having a physical problem. Wrong, wrong, wrong. Whether it’s the result of a chemical imbalance, wrong hormones being produced or even something no one is really sure about as of yet, it is still a real, physical problem.
But this physical problem affects your brain, and your brain is YOU. Your emotions are the results of chemicals being produced! So when something goes emotions go wrong, your emotions, your thoughts, your personality changes too.
If you have chronic pain, you are still you. If you have depression, you are still you, but your emotions and personality are being changed inside you. I am still me, but my illness means I am constantly fighting to retain myself.