The study was obviously a bit skewed and measured "depressive symptoms" together with cortisol, b/c nobody would publish a study that claims cortisol single-handedly causes depression. However, even without the causality conclusion, given what Ray has written about chronically elevated cortisol and depression, I think this is a nice validation of the "stress-depression" hypothesis first proposed by Selye, Pauling, etc.
http://www.cam.ac.uk/research/news/biom ... -treatment
http://www.cam.ac.uk/research/news/biom ... -treatment
