Hi Carolyn
I don't personally know how effective these drugs are, only to say that medical science is on the right track with treating depression. Meaning they are making the connection between stress hormones and depression and finding ways to treat this pharmaceutically.
High cortisol levels are synonymous with stress -- if you have a deregulated stress response then it is likely (as you have established already) that you will have abnormal cortisol levels, hence depression and other symptoms.
However -- cortisol is not the only hormone or bio-chemical to become unstable when there is an deregulated stress response, thus, in my own opinion, these drugs may be too narrowly focused and might not get to the root of the problem either. The only way to find out is to undergo treatment under doctor supervision.
The more natural route is of course naturopathic, i.e. stress management, nutrition, supplementation, exercise and hydration.
Here are some interesting articles for you re. your question (if you have not read these already):
http://www.psycport.com/news/1999/09/27/Ascribe/harvest_Ascribe93849340891112794.html
http://www.depression.org.uk/main/pdf/cortisolstressdepression.pdf