It's natural to feel that way. I agree that he should be told, but I would also give yourself a little time to learn about the disorder first. The book in my signature is excellent and is written for family and friends of those diagnosed. He may be interested in reading it after you let him know.

If there is a BP education group in your area I would suggest both going to that. You can speak to the Psychiatrist about any BP groups in the area. You may also want to check out this website (Depression and Bipolar Support Alliance)
http://www.dbsalliance.org/site/Page...?pagename=home

The mood disorder society of Canada has a good information book on BP that's free to download:

http://www.mooddisorderscanada.ca/