 Bariatric surgery is the treatment of choice for morbid obesity, but it does not lead to equal results in every patients. Research about personality factors involved in successful outcome after bariatric surgery has led to contrasting results. The existing literature about potential predictors of success after bariatric surgery is far from conclusive. The investigators want to evaluate preoperatively by standardized diagnostic interviews MINI, SCID-II and rating scales and questionnaires to assess co-morbid psychopathology. The same evaluation will be done after 1,2 and 5 years. The investigators will look for a relationship between psychological variables and success after bariatric surgery, including amount of weight loss, psychiatric comorbidity, quality of life and employment. The investigators will also investigate the purpose of an pre- and postoperative psychological intervention. Patients on a waiting list for bariatric surgery are randomised to an intervention- and a control group. The intervention is based on cognitive behavior therapy and mindfulness, 6 weeks preoperative and two weeks postoperative programme. Outcome measures are amount of weight loss, psychiatric comorbidity, quality of life and employment. 