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World J Gastroenterol. Jul 7, 2007; 13(25): 3430-3437
Published online Jul 7, 2007. doi: 10.3748/wjg.v13.i25.3430
Role of classical conditioning in learning gastrointestinal symptoms
Ursula Stockhorst, Paul Enck, Sibylle Klosterhalfen
Ursula Stockhorst, Institute of Psychology, General Psychology II and Biological Psychology, University of Osnabrueck, Osnabrueck, Germany
Paul Enck, Sibylle Klosterhalfen, Department of Psychosomatic Medicine and Psychotherapy, University Hospital Tuebingen, Tuebingen, Germany
Author contributions: All authors contributed equally to the work.
Correspondence to: Professor, Dr. Ursula Stockhorst, Institute of Psychology, General Psychology II and Biological Psychology, University of Osnabrueck, Osnabrueck, Seminarstr. 20, D-49074 Osnabrueck, Germany. ursula.stockhorst@uni-osnabrueck.de
Telephone: +49-541-9694078 Fax: +49-541-9694922
Received: February 9, 2007
Revised: February 11, 2007
Accepted: March 12, 2007
Published online: July 7, 2007
Abstract

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 is summarized. 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.

Keywords: Cancer patients; Classical conditioning; Anticipatory nausea and vomiting; Post chemotherapy nausea; Motion sickness; Cortisol; Tumor necrosis factor-α; Gender