Hypnotherapy has a growing evidence base, particularly for anxiety, some forms of chronic pain, and gut-directed work with irritable bowel symptoms. The research is strongest in meta-analyses of trials, which is where you would want it, and it still varies by condition and by whether hypnosis is used alone or with other psychological methods. Stage myths are not data. Clinical hypnosis in these papers is a guided, consented state, not entertainment. Neither finding is a guarantee that trance will reach your particular habit.
Valentine, K. E., Milling, L. S., & Clark, L. J. (2019), The International Journal of Clinical and Experimental Hypnosis. A meta-analysis of 17 trials found hypnosis was associated with larger anxiety reductions than control conditions, with the average participant improving more than about four in five controls by the end of treatment, and the benefit still present at follow-up.
Langlois, P., Perrochon, A., & David, R. (2022), Neuroscience and Biobehavioral Reviews. A systematic review of randomized trials found hypnosis was associated with moderate reductions in pain intensity and pain interference for adults with chronic musculoskeletal or neuropathic pain, with clearer effects when treatment lasted at least eight sessions.
Black, C. J., Thakur, E. R., & Houghton, L. A. (2020), Gut. A network meta-analysis of psychological therapies for irritable bowel syndrome found gut-directed hypnotherapy among the approaches associated with remaining less symptomatic after treatment, alongside CBT-based interventions, while noting a high risk of bias in many trials.