It turns out pain isn't always the same. What hurts me a whole lot may not hurt you so much.

Consider the experiment done recently by researchers at the University of Michigan. They injected volunteers with a saline solution in their jaw muscles, simulating TMJ. If you have TMJ, a jaw condition brought on by stress, you know it hurts. Everybody agreed the imitation TMJ was an unpleasant experience. But, interestingly, for some folks that's all it was--unpleasant. Others were in a world of hurt. So why did some people feel pain more than others?

Here's a clue. Subjects in this experiment were given their injections while lying down in PET scanners. A PET scanner is a machine that allows scientists to monitor your brain activity. And in the folks who reported feeling the most pain, they found the least amount of endorphins. Endorphins are naturally occurring pain-killers. Having more of them means pain doesn't bother you as much.

Okay, so why are some people able to make more endorphins? It's probably in our genes. Researchers have found a gene that seems to be responsible for pain sensitivity. There are several steps in the chain of biological events that occur between having a particular gene and experiencing pain a certain way, but the link has been established. In fact, the best data we now have suggests that one fourth of the population of the United States has the genetic sequence that makes them most vulnerable to pain.

So, next time you're about to call someone a wimp for whining about a little bee sting, remember--they may feel an entirely different pain.