When a friend was hospitalized for appendicitis, people flocked to visit him at the hospital. When I was clinically depressed, some who knew it avoided me like the plague. But I completely understand -- it's natural for us to be afraid of the unfamiliar, including unfamiliar illnesses. And when it comes to depression, people are wary not because they are afraid it might be contagious (hey, many don't even recognize it as an illness!), but because they are afraid of saying the "wrong" thing.
A friend once apologized to me, "I'm sorry I haven't been reaching out to you or being there for you. I'm not like J -- I wish I were, but I'm not. But know that I've been praying for you, okay?"