Opreational definition of anxiety

Anxiety is best defined in terms of the body's responses to adrenaline, the "fight or flight" hormone. Stress makes the heart rate increase, and increases the breathing rate. Thoughts race, and often dwell on negative things like worry and fear. The stomach churns, and muscles feel weak and may tremble. This response was designed to help animals bolt away from danger and escape. However, since humans have very few natural predators any more, our anxiety response has become more of a problem than a help to us.