<qa>  What is the primary endpoint of the study?Our study aims to assess the impact of the hypno-analgesia treatment of IBS on sympathovagal balance. The investigators propose to realize in 7 to 18 years old children with IBS a single center prospective study to highlight after a standardized hypnosis program, changes in the time and frequency domain indices of heart rate variability and clinical or quality of life parameters. The primary endpoint will be the high frequency HF indice. Secondary endpoints will be the other indices of HRV Ptot, VLF, LF, ratio LF HF, SDNN, SDANN, pNN50, RMSSD, the Quality of Life Questionnaire values PedsQL TM 4.0 a pain scale and the composite score of Francis. 