What is stress?

Stress is a little bit like pornography in the following specific sense: you know exactly what it is when you see it, but it can be a little bit hard to define. What is stress? What makes something a stressful experience as opposed to simply being intense? What is the difference between good stress (eustress) and bad stress?

Peter Levine, PhD is the developer of a naturalistic approach to the resolution of trauma called Somatic Experiencing®. In his 1976 dissertation, Accumulated Stress, Reserve Capacity, and Disease, he defines stress as: a reaction resulting from stimuli which sufficiently activate the autonomic nervous system (ANS) and is either resolved or accumulated depending on whether the pre-stimulus baseline is re-established or not.

Let’s break this sentence down into its component assertions. Stress is a reaction resulting from a stimulus: something that happens. Most people think of stress as a response to an external event, but a stimulus can also be internal. It can be an endogenous event in the body, such as an illness. It could also be an emotion that we don’t know how to be present with. So let’s just begin with this notion that something happens. Levine says that it sufficiently activates the autonomic nervous system. The autonomic nervous system is the neural architecture of the mind-body connection. It is responsible for (1) regulating the internal milieu, and for (2) surfacing various energy-processing templates in response to experience. These energy processing templates are autonomic states. They are sort of like the sliders on a graphic equalizer that turn certain frequencies up and certain frequencies down to control the sound coming out of a stereo.

The genius of biology is the efficient use of energy. Our autonomic nervous system is the aspect of our neurology with the most direct relationship to our survival, which is to say the deepest deployment of available energy, and so it’s modulation of these deep levers governs many facets of our moment-to-moment experience. The ANS governs the subjective experience of visceral state, which is to say plainly how it feels to be in our bodies in any given moment. It governs the range of emotional response available to us. It governs the type of thoughts we can have. It governs our perception of the world around us. It governs the range of behaviors with which we respond.

Furthermore, autonomic states that we habitually reside in we begin to experience as existential. If my body moves easily into a flight response and stays, I begin to experience myself as an anxious person. I know myself through the lens of the states that become habitual to me.

So returning to Levine’s definition: the experience we are having is of sufficient intensity or relevance to cause the autonomic nervous system to activate an energy processing template. The body has a finite number of these: they are combinations of threat detection, recruited neurology, and pervading neurochemistry.