I think co-workers are just that: co-workers. From my experience, I believe that they dont care, as long as you dont rock the boat, as long as you do your work, that is all they care about. Most people do not understand depression and do not know how to deal with a depressed person.
Do what is right for you, you are important and you have to take good care of yourself.
This might sound harsh but I am really talking from experience, the workplace is a difficult place to be when suffering from depression!