I was a member of the American Society of Clinical Hypnosis for many years and, while a hospital administrator, got pains in my neck at the end of the day. A year later I interpreted this as reflecting some of my employees being a pain in the neck which they were. An ASCH entire journal issue was on cancer and hypnosis and I used one of the article's research protocols (the article related stress to the immune system and the tendency to develop cancer) to make a ten-minute tape which I then used twice and, low and behold, my neck pain disappeared.
Years later, when a nurse at my (stressful) job found that my blood pressure was high, an internist I had known since adolescence recommended that I take it as often as possible, there being no way that I would take medication. I did, used the self-hypnotic relaxation CD repeatedly daily and graphed my readings. My blood pressure readings gradually went down over several months to superb readings (low 120s over low 70s or better) and have remained so. I'm a great believer in the efficacy of hypnosis, considering it not a learned reaction but fostering the entrance into a different physiological state, this "drop" being experienced by many. Napping using self-hypnosis is far more restful too, a 1/2 hour nap, upon awakening, feeling like a several hour ordinary period of sleep.
I've since used the tape (now a CD and on my Android phone) daily and given it to all of my adult patients without charge for relaxation, though hypnosis is useful for far more. I regard hypnosis as mostly best for physical conditions such as alleviating the pain of childbirth, burns, and back ache; to lower high blood pressure along with the use of a digital blood pressure measuring device as a biofeedback mechanism; for sleep difficulty; to reduce the stress of asthmatic children so they're less likely to have an asthma attack, and with similar issues.
On the whole, apart from relieving stress and anxiety, I believe that hypnosis, and mostly the teaching of self-hypnotic technique which is quick, isn't particularly useful when coping with specific trauma. Here, psychological education about its nature and psychodynamic interpretation of the trauma residue would be most beneficial. It is also far safer than the use of medication.