Self-inflicted Pain Effect, Decreased Sensitivity to

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Definition[edit]

(Braid and Cahusac’s term.)

This is a self-stimulation pain reduction effect. It is the phenomena in which a painful stimulus feels less painful and feels more tolerable when it is self-applied than when applied by other people such as medical personnel. This effect can be substantial. (Decreased sensitivity to self-inflicted pain. Laura Braid, Peter M.B. Cahusac. Pain. 2006 Sep;124(1-2):134-9 available online at: http://www.academia.edu/3559631/Decreased_sensitivity_to_self-inflicted_pain.)

Relevance to fibromyalgia[edit]

In the clinical experience of the author, it modulates pressure algometry readings in some fibromyalgia patients.

Office method of testing[edit]

It has been tested in fibromyalgia patients in the following manner: The patient is seated in a chair with the volar surfaces of their arms on an arm rest so that the lateral epicondyle tender points are facing upwards. First, the examiner holds a hand-held mechanical algometer and presses its tip against the left epicondyle tender point. Pressure is applied gradually, increasing by approximately 1kg per second. The patient is instruct to say “now”, at the instant their sensations pass from discomfort to painful.

This yields a pressure pain threshold (of for example 1.2 kilograms in a severe patient.)

Two minutes later the patient is asked to test themselves by holding the algometer in their right hand and pushing its tip against their own left epicondyle tender point. During this part of the test the examiner should say “I am stepping back”. Then they step back 6 feet to cue the patient that they are at a safe distance. The patient when examining themselves, might get a reading of say 1.8. (This of course it varies from person to person.) In other words, their tolerance to pain was improved during self-examination.

Some patients are surprised by the findings. Some tried to explain it away by saying that the examiner pushed differently.

Author’s theory[edit]

It seems likely that when they do it on themselves, they realize they are in control of the process and therefore safer. This realization likely has a pain modulating effect. Perhaps this relates to evaluative processing of the situation by the patient. In other words, the brain may process pain differently when the party inflicting it is another person. We know we cannot control others, so it is inherently less safe. This could be called a “stranger danger” phenomenon. There may be a “top down” modulating affect on the pain experience. Evaluative processing is believed to at least partially involve the frontal lobe. (In the eye of the beholder: internally driven uncertainty of danger recruits the amygdala and dorsomedial prefrontal cortex. Zaretsky M, Mendelsohn A, Mintz M, Hendler T. J Cogn Neurosci. 2010 Oct;22(10):2263-75. doi: 10.1162/jocn.2009.21402, https://pubmed.ncbi.nlm.nih.gov/19929759/.)