WE epidemiologists hold the short straw when it comes to perks of the job. Many of our colleagues in other branches of science get to travel to exotic climes, hunting out their subjects among coral reefs or deep within majestic rainforests. But our interest is the study of diseases within a human population, and the natural habitat of our specimens is the city, not the beach. This is particularly true for those like me whose specialty is whiplash injury, the neck pain that follows traffic accidents 鈥� especially the low-speed accidents that happen in urban areas with lots of traffic jams. Bye-bye Barbados, hello Manchester.
So what is it about whiplash injury that surpasses my appetite for Caipirinhas at sundown? Whiplash injury was named for the whip-like motion of the neck caused by your head merrily continuing at 50 kilometres per hour unaware that the lorry ahead has brought your car and the rest of your body to an abrupt halt. For most people, things start to get better before the respray job on their car is finished. That鈥檚 most people. A small but significant proportion find that the pain does not go away, long after the injury to their neck muscles has healed. This persistence of pain in the absence of physical damage is known as chronic pain, and it is the reason why I am so interested in whiplash injury.
The concept of chronic pain runs counter to what students learn about pain in the biology classroom 鈥� that it is the body鈥檚 way of yelling, 鈥渟omething is damaged!鈥� In reality, the signals of distress fired off by the sensory neurons are just one of myriad messages that our brains must process before we feel pain. Emotional, cognitive and even hormonal processes are all thought to modify the sensory message. Pain really is all in the head.
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Putting more links in the chain between physical stimulus and brain was evolutionarily a good thing. It allowed us to override pain when we didn鈥檛 have the luxury of time to deal with it. The flip side is that in disassociating the stimulus from the brain, it becomes possible to experience pain without a physical source 鈥� and there you have the potential for chronic pain.
Not having a physical basis for chronic pain makes it incredibly difficult to treat. It also makes it hard to substantiate, leading some researchers to question its existence. This is a particularly contentious issue when it comes to claiming compensation from insurance companies for whiplash injuries. Is it possible that chronic pain is no more than a fantasy, dreamed up to gain not only cash, but also sympathy?
Intriguingly, certain groups of people 鈥� including demolition derby drivers and the populations of Lithuania and Greece 鈥� appear never to suffer chronic pain after whiplash injury. Tellingly, these groups are also barred from claiming compensation. On the other hand, it has been shown that chronic pain does not magically disappear once compensation has been paid. Could it be there are other things that set derby drivers and other groups apart, and that in these other things lies the secret of what causes chronic pain?
This is what a team of us set out to investigate in November 2001. We asked people who had just had a whiplash injury to complete a questionnaire describing what happened. We also asked them whether they were claiming compensation. In addition, the questionnaire measured some of the psychological processes that the brain is thought to use to process pain, such as how well they cope with pain and how sensitive they are to symptoms. We are now comparing the answers of those who still have pain with those who are recovered. In this way, we hope to begin to understand not only what causes chronic pain, but also how to treat those who suffer it. That is quite a tall order, but it makes missing out on the odd palm-fringed sunset no longer seem like such a raw deal.
