This is so sad. I don't have advise to offer, but I do have so much compassion for you. We definitely haven't had to deal with this in my family--none of us can ever seem to shut up, ha! But when my depression starts to take over me, I do "shut down." I stop talking, I start staring off into space and no matter what happens, I just can't seem to open my mouth. My brain will be reeling, chattering out sentences and paragraphs, but they won't go to my tongue. When I was in the hospital, the psychiatrists said it was a normal way for some to deal with depression, but in real life, it frustrates and angers people when I just stop talking. I was heavily bullied as a child and would spend recess and lunchtime sitting in the bathroom silently, trying to hold my breath so no one heard me in there. I actually did that up to high school, spending lunch in the bathroom because people were so mean to me. It's so difficult to read a child when they shut down. I really wish you the best of luck and I hope your little guy starts feeling better soon.