hey, there has yet to be a way to correctly measure serotonin for depression, because the chemical breaks down very quickly as it hits the blood, the rest of it is in your brain and is made by a lot of different reactions. Interestingly enough, they do blood tests for serotonin for digestive system cancers but not the actual amount as its impossible to gauge how much you have running around your system.
I have found that a combination of medication, and group and one-to-one therapy have helped me a lot. I haven't used the NHS apart from my GP as i have private health care, who have been absolutely brilliant for me (and i have spent thousands and thousands in the last year from it!)
For me CBT didn't work, I couldn't get my brain around thinking differently and analyzing my thoughts because I had already analysed them and this was the best course, so I just kept arguing my point with the therapist! I now have a very very intelligent therapist who keeps outsmarting me and my arguments %^& which is frustrating! He manages to get my thoughts all tied up and confused so they go away, plus using EMDR has helped get rid of some of the trauma of the events that have happened to me, now, to be honest I'm not sure what we are working on! Anger i guess. Guess I'll find out tomorrow evening when i go!