Over the past 2 years, a seemingly simple yet perplexing request has preceded most of my encounters with medical professionals: “Rate your pain on a scale of zero to 10.”
As a trained physician who has posed this very question to patients thousands of times, I grapple with how to quantify the sum of my sore hips, prickly thighs, and the numbing, itchy pain near my left shoulder blade. I pause and then, somewhat arbitrarily, choose a number. “Three or four?” I venture, knowing the real answer is long, complicated, and not measurable in this one-dimensional way.
Pain is an elusive phenomenon. It can burn, drill, or manifest as a deep, muscle-clenching ache. My pain varies with my mood and attention, often receding if I’m engrossed in a film or a task. Yet, pain can also be so disabling that it cancels vacations or leads people to opioid addiction. Even extreme pain, like that experienced during childbirth, can be bearable when it has a purpose. But what purpose do my lingering pains from a head injury serve?
The concept of reducing these shades of pain to a single number dates back to the 1970s. The zero-to-10 scale became ubiquitous during the “pain revolution” of the ’90s, when new attention to addressing pain — primarily with opioids — was heralded as progress. Today, doctors have a fuller understanding of treating pain and the terrible consequences of readily prescribing opioids. Now, they are also learning how to better measure and treat the various forms of pain.
About 30 years ago, physicians who advocated for opioid use gave new life to pain management, a previously niche specialty. They pushed for pain to be measured at every appointment as a “fifth vital sign.” The American Pain Society even copyrighted the phrase. Unlike other vital signs — blood pressure, temperature, heart rate, and breathing rate — pain had no objective scale. The society encouraged the use of the zero-to-10 rating system. Around that time, the FDA approved OxyContin, a slow-release opioid painkiller by Purdue Pharma, which aggressively marketed opioids as an obvious solution.
In an era when pain was often ignored or undertreated, the zero-to-10 rating system seemed like an advance. Morphine pumps were unavailable for cancer patients in the ’80s, even those in agonizing pain from bone cancer. In the emergency room where I practiced in the early ’90s, prescribing even a few opioid pills was a hassle, requiring a special prescription pad and state tracking. Regulators rightly worried that handing out narcotics would lead to addiction, leaving some patients without needed relief.
As pain doctors and opioid manufacturers campaigned for broader opioid use, prescribing the drugs became far easier and was promoted for all kinds of pain, from knee arthritis to back problems. As a young doctor, I joined the “pain revolution,” frequently asking patients to rate their pain on a scale of zero to 10 and writing numerous prescriptions weekly. Monitoring “the fifth vital sign” quickly became routine in the medical system. A zero-to-10 pain measurement became a necessary box to fill in electronic medical records, and regular pain assessment became a prerequisite for medical centers receiving federal healthcare dollars. Medical groups added pain treatment to their list of patient rights, and satisfaction with pain treatment affected post-visit patient surveys, influencing reimbursement from some insurers.
However, this approach had clear drawbacks. Studies showed that measuring patients’ pain didn’t result in better pain control, and doctors often didn’t know how to respond to the recorded answer. Patient satisfaction with pain discussions didn’t necessarily correlate with adequate treatment. Meanwhile, the drugs fueled the growing opioid epidemic, with research indicating that an estimated 3% to 19% of people who received a prescription for pain medication developed an addiction.
Doctors wanting to treat pain had few other options. “We had a good sense that these drugs weren’t the only way to manage pain,” Linda Porter, director of the National Institutes of Health’s Office of Pain Policy and Planning, told me. “But we didn’t understand the complexity or alternatives.” The enthusiasm for narcotics left many types of pain underexplored and undertreated for years. Only in 2018, when nearly 50,000 Americans died of an overdose, did Congress start funding the Early Phase Pain Investigation Clinical Network (EPPIC-Net) to explore pain types and find better solutions. This network connects specialists at 12 academic centers to jump-start new research and find bespoke solutions for different kinds of pain.
A zero-to-10 scale may be useful in certain situations, such as adjusting medication doses for hospitalized patients. Researchers and pain specialists have tried creating better rating tools — dozens, in fact — but none adequately capture pain’s complexity. The Veterans Health Administration developed a survey with supplemental questions and visual prompts, but it took longer to administer and yielded no better results than the zero-to-10 system. By the 2010s, many medical organizations, including the American Medical Association and the American Academy of Family Physicians, rejected not just the zero-to-10 scale but the entire notion that pain could be meaningfully self-reported numerically.
In the years opioids dominated pain remedies, a few drugs like gabapentin and pregabalin for neuropathy, and lidocaine patches and creams for musculoskeletal aches, became available. “There was a growing awareness of pain’s incredible complexity — that you would have to find the right drugs for the right patients,” Rebecca Hommer, EPPIC-Net’s interim director, told me. Researchers are now looking for biomarkers associated with different kinds of pain to use more objective measures in drug studies. A better understanding of the neural pathways and neurotransmitters involved in pain could help design drugs to target them.
Any treatments from this research are unlikely to be blockbusters like opioids; they will be useful to fewer people by design, making them less appealing to drug companies. EPPIC-Net helps small drug companies, academics, and individual doctors conduct early-stage trials to test promising pain-taming molecules, aiming to get new drugs approved by the FDA more quickly.
The first EPPIC-Net trials are just starting. Finding better treatments is challenging, as the nervous system is a largely unexplored universe of molecules, cells, and electronic connections. The 2021 Nobel Prize in Physiology or Medicine went to scientists who discovered mechanisms allowing us to feel basic sensations like cold and hot. In comparison, pain is a hydra. A simple number might feel definitive, but it’s not helping anyone make the pain go away.