As with other subjective experiences, such as love, fear, or anger, there's no way to objectively measure pain. We asked Sean Mackey, MD, PhD, chief of the Pain Management Division and associate professor of anesthesia at Stanford University School of Medicine, to explain the unpleasant sensation we all feel in different ways.
1. What is pain?
Pain is such a simple word, but the problem is that what people think it means is not really what it means. All of my patients tend to associate what's going on in their arm or their back as pain out there in the body. But it's not. It's something we call nociception -- electrochemical signals generated in our body in response to injury that get transmitted along nerve fibers to our spinal cord and up to our brain, where they're processed and become the experience of pain.
For example, if you cut your finger, that's not pain in your finger, that's nociception. But nociception is such a terrible word; it doesn't exactly roll off the tongue, and it's not easy for people to remember.
Pain can be an acute event, which signals there is harm and you need to get away from it. Unfortunately, when pain becomes chronic -- when it's present for long periods of time after the tissue has healed -- we can still have this perception of pain even though there is no obvious tissue damage or injury. At that point, pain fundamentally causes rewiring and alterations in our nervous system.
2. What are common myths about pain?
One is that it's all in your head. This has some basis in truth, but we have to be careful. Yes, pain is all in our brain, but that doesn't mean it's made up. I spend a lot of time with my patients validating their experience of pain and then helping them understand how pain really is influenced in the brain by a multitude of factors -- stress, anger, catastrophizing, anxiety, belief systems, expectations -- all of these play a significant role in our experience of pain.
Another myth is that you have to live with it. We need to first find out if there are any medical causes that can be corrected for someone's pain, so it's not just a matter of telling someone you have to live with it. But it's up to us physicians to show people how to best manage that pain, whether through medication, surgery, physical and occupational therapy, or mind/body approaches -- all of these show significant benefit in reducing patients' pain and helping them improve quality of life and physical functioning.
One other myth is that patients sometimes think medication is going to cure pain. Most of the time, medications help reduce or alleviate patients' pain, but in very few cases do they have disease-modifying properties. The truth is, for many of these chronic painful conditions, we haven't found specific cures for the pain, but we have found wonderful ways to manage it.
3. Is chronic pain different for men and women?
Yes. This is a hot topic right now. What we know is there's a larger percentage of women who experience chronic pain --the data in my clinic is two-thirds women to one-third men. Women are more likely to get certain chronic painful conditions, such as fibromyalgia and irritable bowel syndrome. Some conditions tend to affect men more, such as cluster headaches.
Women are also more sensitive to experimentally evoked pain (pain produced in a laboratory or research study) -- heat, cold, electrical stimuli, pressure. But we have to be careful not to interpret this increase to mean that women are weaker than men because there are genetic, hormonal, and central brain differences in women that we believe may be playing a role.
4. What promising new drugs or treatments are on the horizon?
Researchers are working on gene therapy approaches to chronic pain, using viruses to turn on and off our own internal chemical plants to release pain-relieving substances. An example of this is when you get a runner's high: You can have gene therapy that turns that on continuously. These are still in the early stages, but they hold promise.
Scientists are investigating different ways of implanting stimulators into our nervous system and into our brain to turn off the signals responsible for pain. I think we're going to be seeing exciting treatments for chronic pain in the future.
5. What do we now know about pain that we didn't a few years ago?
The mind and body are very linked, and research is showing that linkage more and more.
Recently, we developed technology [a type of MRI scan called fMRI, or functional magnetic resonance imaging] that allows us to focus on a specific region of the brain responsible for the perception of pain. We had people think about their chronic pain as being this terrible, horrific experience. Then we asked them to think about it in a calming, soothing, pleasant manner. We found their brain activity went up and went down as a consequence. They could see their brain activity, and over time they would eventually learn how to control a specific area of their brain and their pain.
Even so, we're still predominantly using fMRI as a way of better understanding the brain and its relationship to pain, but it's not yet ready for prime time as a treatment. We're just at the tip of the iceberg in understanding the role of the brain in pain.