Best to lean on the medical side of it. "I have a chemical inbalance in my brain and this is how it works...(pick your fav book/website/brochure but keep it general). Keep them medically oriented. Diagrams are good tools for this. Then tell them a little about your treatment plan. Then just say that you wanted to let you know. If they get into all that stigma stuff say fine. Was just letting you know. You can't really know what the outcome will be, but your objective was an informative one not a confrontational one. Good luck with this!