The previous definition, published in 1979, defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
The updated definition offers a more nuanced, systemic view of pain, and aims to change the way pain is understood, communicated, and treated.
IASP also added six notes that expand on the definition of pain from multiple different angles. These include:
Pain is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors. Pain and nociception (which is often caused by an outside stimulus) are different phenomena, and pain cannot be inferred solely from activity in sensory neurons. Through life experiences, people learn the concept of pain. A person’s report of an experience as pain should be respected. Although pain usually serves an adaptive role, it may have adverse effects on function and social and psychological well-being. Verbal description is only one of several behaviors to express pain, and an inability to communicate does not negate the possibility that a human or a non-human animal experiences pain.
IASP also added the etymology—origin of a word and historical development of its meaning—of the word pain in order to provide further context.
What Does This New Definition Encompass?
The changes introduced by this new definition, penned by a 14-member multinational Presidential Task Force with broad expertise in pain-related science, may seem subtle. But they lessen the importance of being able to describe pain in order to obtain a diagnosis.
Pain is expanded to encompass people who can’t verbally communicate it, such as infants, adults with dementia, or anyone with speech or language impairments. This way, the spotlight shifts away from how pain is being processed by others and back to the person experiencing it.
“Research over the last 40 years since the prior definition was put in place has deepened and broadened our understanding of the experience of pain and the mechanisms that drive it," Marnie Hartman, DPT, CSCS, an Alaska-based physical therapist and Yoga Medicine instructor, tells Verywell. “I think the new definition demonstrates the complexity and individuality of pain.”
IASP notes that not all pain is linked to evident tissue damage and that pain can stem from multiple sources within the body.
In most cases involving tissue damage, our body sends messages about pain through sensory signals called nociceptors. In the past, the presence or lack of these sensory neurons was used to gauge the amount of pain in one’s body. However, this new definition states that not all forms of pain are communicated using nociceptors. One example is neuropathic pain, which can result from nerve damage or malfunctions in the nervous system. Examples of conditions that can trigger neuropathic pain include phantom limb syndrome, interstitial cystitis, and multiple sclerosis.
“The nervous system is one of the systems involved in the experience of pain, along with the immune system, endocrine system, etc.," Hartman says. “Other dimensions are also present such as genetics, epigenetics, thoughts, beliefs, emotions, and stress responses. Tissue damage may be present, or may have been present at one time.”
This shift focuses on a patient’s experience of their pain, allowing doctors to recognize and believe what they cannot always physically measure. For many who live with chronic pain in the form of an invisible illness, this is an especially validating experience.
“An invisible illness creates the illusion that a person is, in fact, ‘not that sick’ or in some instances, not sick at all," Jaime Zuckerman, PsyD, a clinical psychologist based in Pennsylvania who specializes in the psychological symptoms associated with clinical illnesses, tells Verywell. “When confronted with someone who seems relatively healthy at first glance despite being sick, we assume that they are, in fact, healthy. Being told their symptoms are in their head or ’not real,’ can lead a patient to distrust their own perceptions of their pain or minimize the reporting of their symptoms for fear of being doubted or belittled.”
Spotlighting the unseen aspects of invisible pain opens the door to different diagnostic measures, further focusing on self-reported symptoms. This definition also takes into account the different psychological, emotional, and social components that can influence the experience of pain.
How Can it Guide Treatment Protocols?
The World Health Organization (WHO) and multiple other governmental and non-governmental organizations have adopted IASP’s definition of pain. This new definition encourages medical practitioners to embrace a systemic view of pain when treating a patient.
“Recognizing the multidimensionality of pain especially as it becomes more persistent will hopefully also emphasize the need for multiple care providers to be involved in treatment in order to help shift or lessen the pain experience,” Hartman says. “A deep understanding of the individual and their personal history appears to be the most important aspect in determining who should be the key players on the care team.”
This also allows for more treatment options for pain when the driving factors behind it are harder to pinpoint.
“With this definition, there is more communication and education around pain—what pain is, what drives it, and what we are learning are important factors for treatment,” Hartman says. “And that is all a big promotion of hope for those who are suffering from pain and those who struggle to help provide care.”
For example, Hartman says that adding a mindfulness practice to physical therapy or acupuncture can allow an individual to deeply assess their pain experience and potentially increase their modality of care.
“This provides insight for the individual to further acknowledge and understand some of their own reactions to the pain experience," she says. “They may then learn how to shift some of these or decrease the intensity or persistence of the experience.”
Hartman hopes a deeper understanding of pain can help patients become more involved in their own treatment.
“I think there can be great benefits in a therapeutic relationship and taking time for care,” she says. “Especially when the treatment is delivered with appropriate education of pain science and acknowledging what of the pain experience is actually being targeted, ensuring the individual is an active participant in the treatment delivery.”
