But what accounts for all these differences in how individuals feel and respond to pain? And why are some people, especially women, more frequently prone to disorders like temporomandibular joint pain and fibromyalgia that cause them to feel crippling pain day and night?
Researchers at the University of Michigan believe many answers to these questions lie in the brain -- specifically, how the brain controls our responses to pain.
Now, after several years of using sophisticated brain-imaging techniques that let them see chemical activity in the brain while pain is occurring, the U-M researchers believe they've pieced together some clues to individual pain variations. And what they've found has surprised even them, as they will report on Feb. 18 at the annual meeting of the American Association for the Advancement of Science.
At AAAS, the team will report that gender, sex hormones like estrogen, and genes appear to play a big part in how individuals' bodies, and emotions, react to pain.
In fact, their newest preliminary data suggest that variations in women's estrogen levels -- like those that occur throughout the monthly menstrual cycle, or during pregnancy -- regulate the brain's natural ability to suppress pain.
When estrogen levels are high, the brain's natural painkiller system responds more potently when a painful experience occurs, releasing chemicals called endorphins or enkephalins that dampen the pain signals received by the brain. But when estrogen is low, the same system doesn't typically control pain nearly as effectively.