Since many depressed academics don't like to talk about depression, and especially don't like to tell people they have it, it's an issue many of us face. Many of these responses chime with me, but I think perhaps the one that might be more specialist in academia is "Oh, that's interesting, tell me about it!" since academics are interested in stuff. Not sure whether that is a good thing or a bad thing.
I'll just quote the first paragraph and send you on your way:
I’ve come to the conclusion that most people who have never experienced depression have no idea how to react when I tell them I have a mental illness. They either look away and change the subject, or say some infuriating things. I often bite my tongue to hold back my honest replies. Here is a compilation of my ‘favourites’, and the things I would love to say back but daren’t: