An experimental analysis of classically conditioned nausea during cancer chemotherapy.

This study investigated classical conditioning in women undergoing outpatient adjuvant chemotherapy for breast cancer. Breast cancer chemotherapy outpatients were randomly assigned either to an Experimental Group (exposed to a distinctive stimulus before each infusion of chemotherapy) or to a Control Group. After repeated infusions of chemotherapy, patients' responses to the experimental stimulus were assessed in a location not associated with chemotherapy. Experimental Group patients had increased nausea (self-reported on a visual analog scale) following the presentation of the experimental stimulus at this test trial, whereas Control Group patients did not. Two other measures of nausea corroborated these results. Post hoc statistical analyses confirmed predictions based on conditioning theory. This conditioning model of anticipatory nausea bears witness to the relevance of classical conditioning in clinical medicine.