Iris (Definition) The iris is a structure within the eye that helps reduce the amount of light that reaches the retina. The iris is known as the colored part of the eye, and can be blue, brown, or any color or combination of colors in between. The iris is the portion of the eye that responds to light stimulation. ...Read more.
Scientists also speculate that caffeine may provide a mood-boosting effect that helps ease pain. Regardless of the mechanism by which it works, the data does indicate that caffeine does indeed make pain medications more effective and help ease pain.
People who have quit caffeine tell me they have less anxiety, less anger, and feel less stressed. It may take a month or two after quitting caffeine to feel the full effects of this. Negative emotions such as anger, anxiety, fear, panic and worry can increase muscle tension, leading to pain.