The book you want is The Clinical Effectiveness of Neurolinguistic Programming: A Critical Appraisal
It's quite good. It reviews studies done on NLP approaches to a variety of problems like phobias, PTSD, anxiety, addictions, etc. It includes a discussion of issues with researching NLP and makes suggestions for future research directions.
https://www.amazon.com/Clinical-Effectiveness-Neurolinguistic-Programming-Appraisal/dp/0415635152
I recommend this book: https://www.amazon.com/Clinical-Effectiveness-Neurolinguistic-Programming-Appraisal/dp/0415635152
The R&R Project is taking an NLP technique for PTSD through the studies necessary for VA approval... they are getting cure rates in the >90% range. http://www.researchandrecognition.org/research.html