Placebo responses in patients with gastrointestinal disorders

Over the last several years there has been a growing interest in placebo, not only as an inert control in clinical trials, but also in the placebo effect as a group effect as well as a reaction in individual subjects. Methodological factors such as regression to the mean and natural history of the disease play a role in the evaluation of a possible placebo effect. In this report, we discuss several factors including Pavlovian conditioning, beliefs outcome, expectations, and other factors as potential mediators of the placebo response. Placebo effects are common in gastrointestinal diseases and there seems to be no clear difference between placebo effects in functional gastrointestinal diseases (functional dyspepsia and irritable bowel syndrome) and organic gastrointestinal disease (duodenal ulcer and inflammatory bowel disease).

Role of classical conditioning in learning gastrointestinal symptoms

Nausea and/or vomiting are aversive gastrointestinal (GI) symptoms. Nausea and vomiting manifest unconditionally after a nauseogenic experience. However, there is correlative, quasiexperimental and experimental evidence that nausea and vomiting can also be learned via classical (Pavlovian) conditioning and might occur in anticipation of the nauseogenic event. Classical conditioning of nausea can develop with chemotherapy in cancer patients. Initially, nausea and vomiting occur during and after the administration of cytotoxic drugs (post-treatment nausea and vomiting) as unconditioned responses (UR). In addition, 20%-30% of cancer patients receiving chemotherapy report these side effects, despite antiemetic medication, when being re-exposed to the stimuli that usually signal the chemotherapy session and its drug infusion. These symptoms are called anticipatory nausea (AN) and/or anticipatory vomiting (ANV) and are explained by classical conditioning. Moreover, there is recent evidence for the assumption that post- chemotherapy nausea is at least partly influenced by learning. After summarizing the relevant assumptions of the conditioning model, revealing that a context can become a conditioned stimulus (CS), the present paper summarizes data that nausea and/or vomiting is acquired by classical conditioning and, consequently, may be alleviated by conditioning techniques. Our own research has focussed on two aspects and is emphasized here. First, a conditioned nausea model was established in healthy humans using body rotation as the nausea- inducing treatment. The validity of this motion-sickness model to examine conditioning mechanisms in the acquisition and alleviation of conditioned nausea and associated endocrine and immunological responses issummarized. Results from the rotation-induced motion sickness model showed that gender is an important moderator variable to be considered in further studies. This paper concludes with a review of the application of the demonstrated conditioning principles as interventions to ameliorate distressing AN/ANV in cancer patients undergoing chemotherapy, which is the second focus of our work.

The psyche and the gut

Research on gut-brain interactions has increased over the last decade and has brought about a number of new topics beyond “classical” subjects, such as “stress” and “personality”, which have dominated the psychosomatic literature on gastrointestinal disorders over the past century. These novel topics include brain imaging of intestinal functions, placebo responses in gastroenterology, learning of gastrointestinal symptoms, quality of life in patients with intestinal complaints, and psychotherapy and familial aggregation of functional intestinal disorders. Currently, these new topics appear with a frequency of 1% to 3% in leading gastroenterological journals, either as data presentation or review papers. Increasing focus underlines the importance of enhancing our understanding on how the psyche and the brain communicate in order to better meet the needs of our patients.

不同体位对相对运动错觉诱发运动病的影响

目的观察体位因素对转鼓诱发的相对运动错觉导致的运动病症状是否有影响。方法采用可以变换体位的转鼓作为诱发相对运动错觉进而诱发运动病的装置,对24名健康受试者进行试验。采用恶心评定量表和恶心问卷作为测评工具,观察受试者在不同体位情况下运动病的症状程度和旋转耐受时间是否存在差别。结果卧位体位时旋转后即刻恶心问卷中的消化道不适得分明显高于坐位时的得分,差异有显著性意义(P<0.01)。卧位时受试者的旋转耐受时间较坐位时短,但差异没有达到统计学显著性水平(P>0.05)。男性受试者在旋转后即刻、旋转后15 min、旋转后30 min恶心评定量表得分均高于女性受试者,差异有显著性意义(P<0.05或P<0.01)。结论不同体位对相对运动错觉诱发的运动病症状有影响。

既往运动病易感性对科里奥利加速度耐受性的影响

目的观察既往运动病易感性水平对科里奥利加速度耐受性是否有影响。方法采用运动病易感量表筛选58名不同运动病易感的健康志愿者,采用垂直轴旋转刺激(每秒钟60°顺时针旋转)使身体旋转,以恶心评定量表、恶心问卷和旋转耐受时间为指标观察不同易感者的症状程度和旋转耐受时间的差异。结果既往运动病易感组童年期运动病易感得分、成年期运动病易感得分、运动病易感总分均高于非易感组(P<0.01)。运动病易感组和非易感组旋转耐受时间差异无显著性意义。易感组旋转前、旋转后即刻、旋转后15 min、30 min恶心评定量表得分均高于非易感组,差异有显著性意义。易感组恶心问卷总分、消化道不适得分、情绪困扰得分高于非易感组,差异有非常显著性意义(P<0.01)。既往运动病易感性与旋转耐受时间不相关;与旋转前、旋转后即刻、旋转后15 min3、0 min恶心评定量表得分、恶心问卷总分、躯体不适得分、消化道不适得分和情绪困扰得分呈显著相关。结论既往运动病易感性影响科里奥利加速度耐受性,可作为试验性运动病的预测指标。