I'd rather tell people so they understand me better and so that it can seem less scary. I feel like it can help people understand me and not think in weird. However, I think that it depends on the illness. It's easier to tell people that you have anxiety and depression over something such as an addiction or BPD. I'm covered in scars on my legs from self harm. If some one asks about them, I make jokes, such as telling people that Jaws attacked me, so the mood isn't as heavy.