There is of course 'depression' that is sin, then the downslide to seeking help form secular 'Psychiatry' and therefore the unbiblical definition 'manic depressive' comes into vogue and even worse the dark side of Christian Counselling!
Here are some books at Metropolitan Tabernacle (Spurgeon's Old Church) and look at the blurb from both Dr Ted Williams two books, both worth reading for any who want to help a fellow believer or get to grips with what the Bible teaches about depression:
'Many well-known evangelical authors and churches, however, have turned entirely to the secular remedies and policies in these matters. This book shows what the differences are, including a remarkable review of depression in the Bible, and its relief.'
[URL=http://www.tabernaclebookshop.org/catalogsearch/result/?q=depression]]]CHRIST or therapy[/URL]