Self-inflicted harm as a response to Stress

Point of Curiosity: In an extreme stress situation, is banging one's head against a wall / floor / etc. a common response and if so, why (biologically speaking)?

About twice a year, I briefly and adamantly declare that I'm going to quit my job and dedicate the rest of my life to the study of Endocrinology. Ever since reading The Human Brain by Isaac Asimov in college, I've been deeply fascinated by this system that overshadows our decision-making processes, our interactions, our most basic perceptions of reality.

As a chronic sufferer of PMS (one ovary gives me horrific PMS, while the other one is almost totally symptom-free), I think about Endocrinology a lot. And I'm no longer a teenager; I've been through the experience enough to know that my mood-related symptoms due to PMS feel normal at the time because it's a lot like boiling a frog. The frog's normal evolves with the rising temperature of the water, and my normal evolves with the rising hormones of the over-zealous ovary. I spent years being convinced, at the time it happened, that I was completely justified in reacting to small infractions, only to be ashamed in hindsight. Sure, whatever the thing was, it did bother me, but at a completely different magnitude than PMS would have me believe. Chemicals fundamental to my perception of reality told me I was mad.

Recently, I've been thinking about our stress response a lot. My favourite framing of this comes from Ash Beckham in her outstanding TEDxBoulder Talk "Coming Out of the Closet" who notes:

When you encounter a perceived threat - key word 'perceived' - your hypothalamus sounds the alarm and adrenaline and cortisol start coursing through your veins. [...] this is a totally normal reaction. And, comes from a time when that threat was being chased by a wooly mammoth. The problem is, your hypothalamus has no idea if you're being chased by a wooly mammoth, or if your computer just crashed, of if your in-laws just showed up on your doorstep, or if you're about to jump out of a plane, or if you need to tell someone you love that you have a brain tumor.

I was also struck by parallels between Ta-Nehisi Coates' teenage experience in crack-era Washington D.C. as described in his autobiography The Beautiful Struggle and my teenage experience in a significantly safer suburban neighborhood in eastern Kansas. I was bewildered to find a lot of common ground in the hyper-vigilance we developed in our respective environments, and only the cluelessness of the hypothalamus in stress stimulus could possibly account for it. Our experiences were so wildly different.

To the point of curiosity at hand: I witnessed a self-inflicted head injury - literally banging one's head against a wall - due to a stress response that kept escalating. Warning signs prior to this included full-body shaking and an inability to speak.

And it made me wonder, is this a thing? Does the head-banging have a purpose, one that potentially has some kind of benefit? Could it, for instance, disrupt an escalating stress response in the endocrine system? Is it an instinct to become unconscious, or something else?

My Google Fu isn't always the best, but I quickly found a 2011 article that confirmed my hypothesis wasn't entirely without merit, that this head-banging may have an actual "positive" (for a specific and relative definition of "positive", admittedly) impact on the endocrine system. The journal Psychoneuroendocrinology has an article, "Alterations in the neuroendocrinological stress response to acute psychosocial stress in adolescents engaging in nonsuicidal self-injury", which concluded from a very small trial (28 participants) that women who engage in Nonsuicidal Self-Injury (NSSI) experience reduced cortisol confirmed by a saliva test.

Which, of course, immediately caused me a follow-up question:

What is an HPA Axis?

The HPA Axis is the hypothalamic-pituitary-adrenal axis. Both the organs and their influence and interactions on and with each other make up this axis. This immediately lead me to a model called the General Adaptation Syndrome (yes, GAS) developed by Hans Selye which explains an organism's response to a stressor, real or imagined.

There are three core stages defined in the syndrome: Alarm, Resistance and Exhaustion.

During the Alarm stage, we get the familiar adrenaline rush and our body starts releasing cortisol. Shock happens during the Alarm stage.

During the Resistance stage, the cortisol really ramps up. All kinds of resources get thrown into the bloodstream to help us resist or deal with the stressor.

There's different ways to exit via the Exhaustion stage: either the stressor is eliminated and we enter a Recovery stage, or the stressor remains and eventually our body's resources are depleted.

For another time, my follow-up question from that is, could self-harm be an attempt to abort the Resistance stage before hitting the Exhaustion stage?

I have so much more I want to learn about all of this, but for the moment, my lazy no-libraries-only-internet starter answer is: I don't know if the head-banging is a common response but there's a maybe to it having a potentially cortisol-reducing effect if we can assume self-inflicted head injury is similar to other kinds of NSSI like cutting.