I've had depression and anxiety for about three years now. When applying, I didn't include anything about it in my UCAS application, and I went to uni with no intention to tell anyone, really. In my second week there, I had a meeting with my guidance tutor, and when she asked if there was anything they should know about that might affect me during the year, I sort of just ended up blurting it out. She said she was glad I told her, because most people don't bother letting them know. I found myself quite glad to have informed them, because I ended up missing classes on a lot of my bad days, but they were aware of my circumstances. I think people are more inclined to be open about such things if it means lectures and class time will be missed.