The IASP definition of pain has been revolutionary. It has helped shift the focus away from mechanisms involved in producing the experience we all know, towards defining the nature of that experience. The definition is relatively simple, easy to remember and contains several important qualitative definitions that are integral to the experience. For those of you who haven’t attended one of my classes, the definition is:
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Note: The inability to communicate verbally does not negate the possibility that an individual is experiencing pain and is in need of appropriate pain-relieving treatment. Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. Biologists recognize that those stimuli which cause pain are liable to damage tissue. Accordingly, pain is that experience we associate with actual or potential tissue damage. It is unquestionably a sensation in a part or parts of the body, but it is also always unpleasant and therefore also an emotional experience. Experiences which resemble pain but are not unpleasant, e.g., pricking, should not be called pain. Unpleasant abnormal experiences (dysesthesias) may also be pain but are not necessarily so because, subjectively, they may not have the usual sensory qualities of pain. Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain, and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause.
It was first proposed in 1979, and has not been substantially changed since then, although the accompanying note has.
Now two prominent pain researchers are proposing a new definition: Pain is a distressing experience associated with actual or potential tissue damage with sensory, emotional, cognitive and social components (C de C Williams & Craig, in press).
Their arguments centre on some important aspects that have influenced our understanding of pain and represent advances in scientific understanding of pain since the first definition. The first definition was ground-breaking but acknowledged only sensory and emotional features of pain: our understanding of pain now recognises the influence of and effect on cognitive and social components. These aspects are important because in many ways the original definition seems to discourage clinicians to be aware of emotional, sensory AND cognitive and social aspects of pain in ACUTE pain as well as chronic.
They further argue that pain is more than “unpleasant” if it is clinically problematic, and suggest that “distressing” be used to describe the nature of that experience. And it is this aspect that I am less comfortable with – because, as many readers of this blog know, it is possible to experience pain without distress, particularly if that pain is being managed using approaches such as mindfulness and acceptance. To my mind, a definition that equates experiencing pain with distress risks invalidating those who, because of their understanding of pain, or their social context, or even concurrent competing goals, fail to identify their pain as distressing but instead experience it as “negative but irrelevant”, or those who, because of social context and learning, don’t frame their pain as distressing and present as stoic and calm.
Despite this difference in opinion, the rest of the arguments for changing the definition of pain appeal to me. There is the need to acknowledge not only verbal report, but also nonverbal behaviours as part of the way humans express and communicate their experience of pain. Unfortunately, researchers and clinicians can focus on a single dimension: intensity – although thankfully most effective clinicians will incorporate more than one dimension and include assessment of behaviours, voice, facial expression, interference on daily life, quality of pain etc.
C de C Williams and Craig also propose revising the note. The note is often not included when people are discussing the definition of pain – in fact, one prominent clinician I know declared that “Pain is not a psychological phenomenon” – er…. take a look at the last sentence of the note, please Dr K. As a result, there are those who still do not recognise that pain is not just about nociception and nociceptive pathways. This means some unfortunate patients do not have very real and clinically important psychosocial aspects of their experience attended to, despite years of research showing just how critical these factors are!
Their first recommendation is to remove reference to “pain in the absence of tissue damage… are probably psychological” – because as we know now, neuroplasticity provides an explanation for this phenomenon. Additionally, they note that psychological phenomena exist even in acute pain, such as emotional responses, problematic thinking styles, avoidance, social disruption – and these can all occur with diagnosable tissue pathology. Finally, ruling out prickling, dysaesthesia etc seems to ignore the presence of these as part of many reports of pain.
What would I suggest? I think it’s still useful to use the word “unpleasant”, perhaps it could be relabelled an “aversive” experience, rather than necessarily “distressing” which seems to restrict painful experiences to only those that people identify as distressing – even people who participate in body suspension where the entire bodyweight is carried on hooks inserted into the skin and who experience this as a process in which they may ultimately feel euphoria describe the pain as “aversive” (or, to use their words “It hurts like a bitch”!). Aversive implies the call to action potential that is present in all pain.
My definition? Pain is an aversive experience associated with actual or potential tissue damage with sensory, emotional, cognitive and social components .
DE C WILLIAMS AC, Craig KD. Updating the definition of pain. Pain. 2016. PubMed: www.amedeo.com/p2.php?id=27200490&s=pai&pm=84c33420cb43501