depression is caused by a chemical imbalance in your brain; it depletes your energy and moods because of that imbalance. you don't want to live because you are not getting enough of what your brain needs to feel good. depression causes you to lapse into sadness and feelings of hopelessness.
Brain chemistry affects all the systems in the body, hormone levels, etc. Being sick is always exhausting.
Because if naws away at your very being!
It's a mental state where you get so down, that you can't see a way out of the pain even if the 'door' is wide open. You need help to escape your own mind. Depression is a terrible thing. Feeling sad over something and actual depression are so different you can't even put them in the same basket. Nothing seems worth it, I guess.
Depression has no power that you don't give it... it's just some people concentrate on finding the answer in a bottle or box and not inside.