Pain Is Not Just an Alarm | 医療法人社団EPSDC

1. We may have known far less about “pain” than we thought
The sharp, jump‑inducing sting when you stub your toe. The burning, lingering discomfort after shingles. Or the unresolved feeling when you seek care for chronic low back pain but are told “nothing abnormal” on imaging. Pain is so familiar that modern medicine took a surprisingly long detour to grasp its essence.
Historically, medicine treated pain as a simple mechanical signal—an alarm reporting bodily malfunction. Contemporary pain science, however, reveals a deeper, more subjective world woven by the nervous system’s dynamism. Pain is not the faithful mirror of tissue abnormality we long believed it to be.

2. Pain is not merely a sensation—it is an affective experience
The latest definition from the International Association for the Study of Pain (IASP) overturns common wisdom. Pain is “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.” Crucially, pain is positioned from the outset as an experience that inseparably includes emotion, not just a physical sensation.
“Pain is not a simple phenomenon in which a bodily stimulus travels transparently into consciousness.”
Tissue injury and the distress we feel are not in one‑to‑one correspondence. Pain is interlaced—right from the start—with unpleasantness, aversion, fear, past memories, and the brain’s appraisal of “threat.” The simplistic equation injury severity = pain intensity often fails before the truth of human subjectivity.

3. Descartes’ shadow: Why “pain with normal imaging” is dismissed
Why has pain that doesn’t show up on scans been discounted for so long? A major residue is 17th‑century philosopher René Descartes’ mind‑body dualism.
Treating the body as a machine and the mind as separate fueled explosive progress in modern medicine: objective observation, dissection, lesion localization, surgical breakthroughs, anesthesia. Yet it also left a serious legacy—medical education still leans dualistic, and the biology of pain remains under‑taught. Pain without a “machine fault” (visible lesion) is too often labeled “psychological = not real” and pushed outside medicine’s frame. Patients then suffer a double injury: bodily pain plus social invalidation—“not being believed.”

4. A startling new norm: Pain is not an “input” but the brain’s “output”
The central paradigm shift: pain is not simply the result of peripheral input; it is a constructed output of the brain.
The 1965 Gate Control Theory proposed “gates” in the spinal cord that modulate signal flow, physically opened and closed by descending control (attention, expectation, fear). A soldier, relieved after surviving battle, may feel little pain despite injury, while a crash victim in high anxiety may feel severe pain from minor damage. This is not “all in the head”; it is brain‑driven gate control.
Equally pivotal is Central Sensitization: persistent or intense stimulation sensitizes brain/spinal circuits so they continue outputting pain even with little or no peripheral drive—a disorder of the nervous system itself. Ronald Melzack’s Neuromatrix Theory further shows pain is generated by a brain network integrating memory, emotion, and body schema. Phantom limb pain—pain in a limb that no longer exists—is decisive evidence that the brain itself can output pain.

5. The danger of “not feeling pain”
Wishing pain would vanish is human. But congenital insensitivity to pain exposes a paradox: people who cannot feel pain detect harmful stimuli yet cannot assign them the meaning “danger—avoid.” They fail to protect injuries, compounding damage to catastrophic levels. Pain is both an unwelcome torment and an essential biological defense for survival. Its “unpleasant experience” quality is precisely what drives us to safety.

6. Conclusion: Reframing pain as a “narrative”
Modern pain science’s biopsychosocial model understands pain as an interplay of biological neural responses (Bio), individual psychological states (Psycho), and social factors (Social)—loneliness, uncertain futures, guilt toward family.
Pain can no longer be captured by numbers alone like temperature or blood pressure. Clinicians must listen to the largest data set behind the images—the patient’s words. Pain is not only an event; it is a narrative woven through a life.
Your pain may be a grave trial. It is also an urgent message from your brain—integrating all past experience and present context—struggling to protect you.
What story is your brain trying to tell you through the pain you feel?

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