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The Science of Pain

Medical researchers continue to unravel the mysteries of pain and look for new ways to help patients manage it.

nerve cell and brain

Patients who have rare and serious disease often cope with chronic pain. This is one in an occasional series about the science of pain management

Stated simply, pain is a message from body to brain that something is not right. But anyone who has experienced serious pain, including chronic pain, knows that there’s nothing simple about it. Many doctors would agree. Though research has made strides in understanding pain, it remains a complex and individualized medical challenge for those coping with injuries, illnesses and disease.

When doctors, researchers and patients attempt to describe pain to each other, it can often sound like they’re discussing separate things, said Kalpna Gupta, a scientist at the University of California, Irvine.

Pain is such a complicated phenomenon and it’s experienced so differently by various groups, that even establishing what we mean when we say the word “pain” is difficult, she said at a recent webinar hosted by the National Hemophilia Foundation. But, like an elephant in the room, it’s an issue too large to be ignored.

Pain takes a massive toll on both our bodies and our world at large. Gupta says pain costs the U.S. more than $600 billion a year — more than cancer, cardiac diseases and diabetes combined. People who have bleeding disorders like hemophilia can experience chronic pain, especially in their muscles and joints, due to bleeds and damage that accrues over time. Once pain starts, it can lead to depression, anxiety and the loss of quality of life, and make it more difficult to do things that have been shown to reduce pain levels, like exercise.

What Pain Means

Pain finds us all eventually, whether it’s a twisted ankle or a root canal, or a recurring symptom of a rare disease. Chronic pain, typically defined as pain that lasts longer than six months, affects about 20 percent of Americans, or one-fifth, according to the U.S. Centers for Disease Control and Prevention.

On a physiological level, pain of any sort is transmitted through electrical and chemical signals from our body to the brain. This involves an intricate cascade of biological reactions.

“I call it one of the most complex orchestras,” Gupta said. Despite that complexity, modern medicine approaches pain in an almost rudimentary way.

To deal with pain, she says, there are really just two basic methods. Doctors can stop or treat a disease so effectively that it no longer causes pain. Or doctors can find out how a specific condition or ailment is causing pain, and then try to head off those signals before they can cause discomfort.

The latter strategy is why, for decades, opioids took a leading role in pain management. The powerful drugs work by blocking receptors on nerve cells, inhibiting their ability to transmit pain signals. Opioids treat pain effectively, but they can be addictive, and the spiraling opioid crisis has, in recent years, discouraged their use. Opioids are still prescribed in some cases today, but doctors are careful to assess a patient’s risk of abusing them and supply them in small amounts after something like a surgery.

To fill the void, doctors today are relying on non-opioid pain medications like acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDS), as well as local anesthetic techniques like nerve blocks, which prevent nerves from transmitting pain signals. These methods form the core of what’s called multimodal pain management, a more recent approach that seeks to use multiple strategies at once to treat pain, depending on the patient’s needs.

Cannabis, or medical marijuana, is also getting a close look though some studies have found its effects to be weak.

Looking Beyond the Body

A new framework for treating pain --  called the biopsychosocial approach – has some promise. It treats pain as a biological process that’s intimately intertwined with our psychology and environment. Recent scientific work shows that mental and emotional states have a profound effect on our experience of pain, and that addressing those factors can lead to lasting improvements.

For example, when researchers gave male mice both better diets and the companionship of a female, they had less pain than those without these benefits. The better fed, less lonely mice had higher levels of serotonin, the researchers say, a neurotransmitter that can affect how we experience pain.

In humans, studies show that depression and anxiety can worsen the level of pain someone experiences. Other psychological factors, like how in-control we feel about our pain, and other attitudes also alter perceived discomfort. That’s where a range of treatments, from acupressure to mindfulness to yoga come in. These types of treatments are becoming more common, Gupta said, but doctors may not always know how to prescribe them.

Other research has focused on the benefits of psychological approaches to dealing with pain that help patients reframe their situation and develop mental tools to help them cope. Cognitive behavioral therapy (CBT), a technique that’s been around for decades, has been proven to be of some benefit to certain patients and is growing in popularity as evidence for its efficacy builds.

In CBT, practitioners use exercises like deep breathing, guided imagery sessions and progressive muscle relaxation to create different responses to pain and other negative stimuli. It offers an additional weapon in the battle against pain, says Drew Sturgeon, a professor at the University of Washington Medical School and a licensed clinical therapist.

“We’ve known for about 40 years that the best combination of treatments for pain management is a combination of medicine, physical therapy and psychology,” he says. “CBT and other psychological approaches for pain aren’t meant to replace medicine, they’re meant to supplement it.”

New Strategies for Dealing with Pain

While doctors expand their arsenal of pain treatments, researchers are focusing on the next generation of pain management techniques. Preliminary studies using ultrasound to stimulate certain brain regions indicate it might be an effective, non-invasive treatment for pain.

In one experiment, researchers compared healthy people who either had ultrasound directed at their thalamus, a region of the brain that deals with sensory perception, including pain, with people who had a fake ultrasound treatment. Those who got the real ultrasound performed better on a test of pain thresholds than those who didn’t.

In another study, scientists used ultrasound to perform a procedure called a thalamotomy in people who suffered from chronic pain resulting from nerve damage, called neuropathic pain. The technique destroys tiny, targeted portions of the thalamus to remove abnormally-behaving brain cells. One year later, the patients reported their pain levels had decreased by more than 50 percent.

As research continues, Gupta acknowledged the field of pain remains full of mysteries.

“Pain is like a big elephant in the room with three blind men,” each trying to figure out what it is and how to approach it, she said. Research strides have come more quickly in the fields of cardiac care and cancer treatment.

“Why are we so much behind? The reason is that it is not one system,” Gupta said. To fully understand pain is to understand multiple systems and how they interconnect, including “the overall entanglement of nerve fibers that run from head to toe.”