Second, to be classified as chronic constipation according to the Rome III criteria, patients should not fulfil the criteria for irritable bowel syndrome (IBS). In the present study almost all patients had severe abdominal distension and pain. A placebo effect has been shown to be very important, progressive and long-lasting in patients with IBS. For example, in the trials of tegaserod for constipation-type IBS, placebo produced a progressive improvement over the 3-month duration of treatment. Even more relevant, in non-drug treatments of IBS such as acupuncture, the placebo arm showed a marked and long-lasting improvement in symptoms and quality of life which was comparable to the effective treatment.4 We cannot therefore rule out the possibility that a placebo effect is an important confounding factor in an open study like this on patients who all underwent surgery and who were probably followed up by the doctors who performed the implant.
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