Chronic pain

Pain has been in this wiki since its first ingest, but as an anatomical claim rather than a clinical one. Craig (2002)‘s central move was to reclassify pain as interoceptive — a homeostatic feeling carried by the lamina I pathway and represented in the insula, alongside temperature, itch and hunger — rather than as an exteroceptive submodality of touch. That reclassification is what makes chronic pain an interoception problem in principle. Bonaz et al. (2021) supply what it looks like in practice.

The clinical picture

Chronic pain is defined as pain persisting more than 3 months, or beyond the expected time for healing (Treede et al. 2015, the ICD-11 classification), with broad social and economic repercussions. The conditions grouped under it in the review: fibromyalgia, chronic low back pain, temporomandibular pain disorders, noncardiac chest pain, nonspecific chronic bone pain, and painful somatoform disorders.

The interoceptive finding is short and, unusually for this review, dimensionally specific:

In chronic pain patients, deficits in objective interoceptive accuracy can predict symptom severity. Interestingly, for subjective interoceptive sensibility and metacognitive awareness (insight), data are less conclusive.

That comes from Di Lernia et al.’s (2016) systematic review — the strongest evidence grade cited for any of the review’s somatic conditions. It says accuracy is the dimension that tracks severity, and it declines to claim the other two do. The wiki should keep the asymmetry: this is one of the few places in the clinical literature where a source declines to report a sensibility effect rather than reporting one and over-reading it. See interoceptive-taxonomy.

Where it sits in the comorbidity cluster

Chronic pain is not a separate territory in this account. It appears in three places in the review, and the linkages are the point:

• Among the brain-body disorders sharing anticipatory symptom-related anxiety, central sensory amplification, and aberrant autonomic activation — the three features Bonaz et al. propose as the common interoceptive surface across IBS, functional heartburn, noncardiac chest pain, urological chronic pelvic pain, fibromyalgia and functional neurological disorders.
• As a downstream expression of joint-hypermobility: fibromyalgia is named among the symptom expressions in people with variant connective tissue, alongside cardiovascular, gastrointestinal, respiratory and pelvic manifestations.
• As one of the conditions in which early adversity raises risk, exacerbated by stress — with UCPPS the worked case (linked to EALs, exacerbated by stress, with functional abnormality in a bladder–PMC–locus coeruleus–forebrain pathway).

“Central sensory amplification” is the mechanism term doing the most work across these, and it is essentially the inferential claim: precision on ascending bodily signals is set too high, or the prior encoding a pathological cause is too strong, so ordinary afferent traffic is inferred as pain. The review does not develop it formally; computational-psychiatry is where that machinery lives.

The treatment question, unresolved

Two intervention logics meet here and the wiki holds both without a resolution.

Exposure. Farb et al. (2015) extend interoceptive exposure from panic to chronic pain (Boswell et al. 2013; Zaman et al. 2015) on the argument that some psychosomatic pathology involves fear-conditioned interoceptive avoidance, which attentional distraction reinforces rather than challenges. On this reading more contact with the sensation, held non-avoidantly, is the treatment.

Bioelectronic. Bonaz et al.’s translational close puts antinociceptive effects among the reported benefits of neurostimulation — spinal cord stimulation, VNS, TMS, tDCS, DBS. On this reading the target is the pathway, not the appraisal.

These are not incompatible, but they are different bets about where chronic pain is located in the hierarchy — and the review’s own framing (“perturbation at one level can impact another level”) is precisely the claim that makes the question hard to settle. Bonaz et al. close the section with an aspiration rather than a recommendation: “interoception is an important aspect to consider for future avenues in the development of treatments for chronic pain.”

Note on a tension with the trauma material

The wiki holds stress-induced-analgesia from van der Kolk (1994) — trauma producing reduced pain sensitivity, an opioid-mediated numbing arm running alongside hyperarousal. Bonaz et al. have early adversity raising chronic-pain risk. Both can be true (acute analgesia, chronic sensitization; different timescales, different mechanisms) and neither source addresses the other, but the wiki should not let “trauma dampens pain” and “trauma predisposes to chronic pain” sit on adjacent pages unremarked. Recorded as an open seam.