Definitional issues in the study of anticipatory nausea in cancer chemotherapy.

Biobehavioral research investigating anticipatory nausea in cancer chemotherapy has been hampered by the lack of a consistent and conceptually defensible definition of this phenomenon. The most frequently employed definitions have failed to account for the possibility that reports of pretreatment nausea might be attributable to pharmacological factors. One possibility is to restrict the definition of anticipatory nausea to instances of nausea or vomiting experienced prior to a treatment on Day 1 of a new chemotherapy cycle. The impact of this and previous common definitions of anticipatory nausea on research addressing the issues of prevalence rates and characteristics associated with the development of anticipatory nausea is illustrated and discussed. Overall, researchers are encouraged to reduce inappropriate criterion group heterogeneity through careful consideration of how the presence or absence of anticipatory nausea is defined.