New Scientist vol 136 issue 1845 p6

To find the most effective method to stop smoking, Frank Schmidt and research student Chockalingham Viswesvaran from the University of Iowa conducted a meta-analysis, bringing together the results of more than 600 studies totalling nearly 72,000 people. The results, which were published in the Journal of Applied Psychology and included 48 studies of hypnosis covering 6000 smokers, clearly showed that hypnosis was three times more effective than Nicotine Replacement.