Defining, measuring, and interpreting stress in laboratory animals.

One basis of scientific research with animal subjects is consistency of subject physiology, physical parameters, and behavior. Ideally, selected experimental variables account for primary differences measured between test and control groups. One intangible variable to control is stress experienced by the animals. In common parlance, the word stress is often used to indicate a negative experience. However, stress is not inherently bad, and a stress response should not be assumed to indicate an experience of distress or pain. This paper examines ways in which research animal stress may be defined, measured, and interpreted.