Scot McKnight has a great post titled Burnout for Pastors, which are statistics he has reproduced from Pastors at Greater Risk, H B London, Jr., and Neil B Wiseman, Regal Books, © 2003

Though pastoral ministry is not the only vocation where burnout is present and where many of these statistics can be reproduced….I do think though that pastoral ministry is unique because of the expectations from the congregation, the community, etc. I have worked both in and out of the church and burnout is definitely a danger, and it is especially a danger since many will not seek help because of a feeling of failure, or not living up to the “requirements” and “expectations” of the those they pastor, etc.