Questions Raised by the IASP Pain Definition

Last updated: Thu, Feb 27, 2025

Pain is not, as the saying goes "all in your head," but of course modern science persuades the most skeptical among us that without a head you would feel no pain, or at least not complain about it. That the locus of pain is in your head has interesting implications for how we are able to understand pain and how we are disposed to understand it, whether “we” is you or I, people in general, or doctors and pain researchers.

I have gone into considerable detail to present and contrast physiological and psychological viewpoints on pain. (How Pain Is Made and The Psychology of Pain.) I've tried to point out what is firmly known from the two differing viewpoints and to point out some of the limitations and biases of the viewpoints. The experience of pain is a product of the entire nervous system, and of course the condition of the CNS affects that experience.

Although our knowledge is expanding, still relatively little is known in detail about the role of the CNS, the more rostrally we go. Much of the argument for a strong effect of the brain on our perception of the presence and intensity of pain seems to be based on the the large number of pain patients for whom there is not a clear diagnosis that points to a cause in the body's tissues. It provides an opportunity for strong-mind theories of pain experience.

Some of what is well understood about brain changes in chronic pain is included on the following pages. Additional relevant phenomena were presented in Pain Science 2: Nociceptors and the Spine and Pain Science 3: Neuroscience and the Brain. On the remainder of this page, I present another critical analysis of the IASP pain definition and their related commentary. I attempt to highlight the pro-mind bias of their writings.

According to the International Association for the Study of Pain, who presumably have given this some deep thought, pain is:

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.1

So, pain is an experience with sensory and emotional components. In notes to their definition the IASP committee add that, Pain is always subjective. It isn't always connected to tissue damage, but 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. They add that [m]any 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.

Do they mean to imply that if we disregard the subjective report, then there is a way to distingush the experience of tissue damage from the experience of pain? I suspect not. I suspect that this awkward utterance reflects the collision of the limits of clinical knowledge with the necessity many pain practitioners face of deciding whether pain is "based on tissue damage" or not in the absence of good tests. See Assessment and Diagnosis and numerous other sections for more about the limits of clinical diagnosis.

I would challenge the IASP to provide proof of their assertion that "many people report pain in the absence of ... any likely pathophysiological cause." This seems to me a particularly audacious and misleading claim given what is known about the complexity of pain, given the rate at which knowledge is being added, and given all the gaps in our current knowledge. What is known about pain makes it clear, as it seems to me, that it's very common for pain to be caused by clinically undetectable physiological causes, but that isn't what their statement says. They could easily have constructed a true statement about this by saying that many report pain in the absence of "clinical evidence that establishes a specific cause," but didn't. I suspect that they didn't say this because such a statement points directly at the gaps in our ability to diagnose painful conditions, but that's just me speculating.

So here, in one sentence of definition and a paragraph of clarification, we find several important ideas:

• That pain is fundamentally an experience. How can we think scientifically about an experience? How do we medically treat an experience?
• Pain isn't just any kind of experience, it's an emotional experience. An unpleasant one. This must have some implications, although what implications it has isn't made clear.
• Pain can occur in the absence of tissue damage. It can occur with no "likely" pathological cause. In fact, says the IASP, "many people" report that type of pain. For psychological reasons. Or perhaps people report pain without really feeling any pain at all. The IASP comments are a bit vague.
• Pain is "subjective," whatever that meant to the authors. Perhaps we can add a little clarity....
• We may or may not "take the subjective report."

This is all rather mysterious. Like much that can be said about pain, it raises more questions. As with many perplexities, we can begin with things that we know and see how much mystery is left. I continue that process in this chapter.