We'll look at how from a scientific perspective doctors are still trying to understand the complexities, even mysteries, of how we feel pain. So to talk about the scientific understanding of pain I'm joined by Dr. Jeff mogul. Dr. Mogul welcome to the program.
Thanks very much for having me.
Now this seems like a strange question but what exactly is pain?
Pain is a strange thing. It's sort of like lights which we learned a long time ago was two things at the same time. Pain is at least two things at the same time. It's a sensation - sort of like vision or hearing or touch, but it's also an emotion - like fear or anger. And it's also a third thing at the same time it's a drive state - like hunger or thirst. It's something that demands that you carry out an action.
So why is it so hard then to measure a person's pain?
I think the problem ultimately is that it's completely subjective. It's sort of intrinsically internal to the person in a way that vision and hearing are not. So with vision, there's energy out in the environment. There are photons, and you can measure how many photons there are hitting your eye. And usually the brightness corresponds very very well to the number of photons. But with pain it doesn't work like that at all. There are energies in the environment. There's pressure and there's heat and there's inflammation. But they don't correlate very well at all with the experience, the perception, that people have of pain and pain comes in different forms.
I mean you can have a needle prick and the end of your finger, but you could also have something like back pain or something really serious.
Exactly. You can divide pain up. You can split it into any number of different categories, and when you do so the biological basis completely changes. So there's no heat pain versus mechanical pain. And they're short lasting pain compared to long lasting pain. And there's pain to the skin compared to pain to the muscle compared to pain to the joints compared to pain to the visceral organs. And there's pretty good evidence that all of these things are very very different.
Why does there seem to be such a variability between the way people report pain? I mean somebody might complain a lot about some little thing and other people seem to be able to put up with a lot of pain.
Yeah, this is something that I've been studying practically my whole career. They've done twin studies and I can tell you that almost half the answer is genes. And a little bit more than half the answer are other environmental factors, probably the most important of which being how much pain experience have you had in your life before that.
How much of a variation could there be between one person and another given the same pain stimulus?
Oh an astounding amount of variation. So they've done studies like this. They once took 500 people in Bethesda, Maryland, and they gave them all the exact same thermal stimulus to their forearm and asked them to rate that on a scale from zero to 100. There were a few people at the low end that said that was about a four or a five out of 100. And then there were people at the high end that said it was a 95 or 96 of a hundred and every rating in between. So as much variability as you can imagine, we can demonstrate.
Now you mentioned genetics of pain. How is that influencing how we experience it?
Well on the one hand it's a large part of the answer. We know there are genes that influence pain sensitivity and susceptibility to developing chronic pain disorders and how well people respond to analgesics including the opioids like morphine.
So you're saying that some people are actually more sensitive to pain than others because of their genetics.
Oh 100 percent. It's just that I can't tell you which genes.
You also mentioned experience with pain. How does that come into it.
Yeah it turns out that one of the biggest risk factors for chronic pain and how long it's going to last and how big a problem you're going to have with it is whether you've ever had pain before. And why that is no one really knows. The system is probably sensitized, and each time you have an injury or some sort of insult that causes pain, it appears to make things a little bit worse than it was before.
Okay so other than genetics and your experience with pain from the past, what other factors might influence how we experience pain?
Well the big one is sex and gender, and it is known that women, and this is contrary to what most people guess, but women are in fact more sensitive to pain. They represent the clear majority of pain patients.
Dr. Mogel, thank you very much.
Dr. Geoff Mogel is a professor in the Department of Psychology and Canada Research Chair in the genetics of pain at McGill University in Montreal.