Pull a thread with me · Overwhelm and burnout

The Anatomy & Physiology of Overwhelm

This is a thread: my current understanding, built from the science but not yet fully settled. Tap any Hey Dr. B! line for the science behind it.

1. Your mind and body run on a budget.

   Cellular energy (ATP) is the currency. Your brain keeps a running account: resources coming in (food, oxygen, sleep, rest) and resources going out (every metabolic need, every processing demand). The mind’s most important job is to keep the budget balanced – to make sure there are resources to safely navigate this moment and the next.

2. Interoception is how the brain senses and tracks the body budget.

   We don’t get a readout of our ATP or blood sugar. What we get is a feeling: hungry, tired, calm, on edge. A feeling that, if we listen to it and interpret it correctly, tells us exactly what we need.

   Hey Dr. B! What is interoception?

   Interoception is the sense of the body from the inside: signals from the heart, lungs, gut, blood vessels, immune system and the chemistry of the blood, carried to the brain mainly through the vagus nerve and the spinal cord and mapped in the insula. The brain doesn’t read these signals like a dashboard. It predicts what the body should be reporting and corrects the prediction against what arrives, and the result reaches awareness as a feeling: hunger, fatigue, calm, unease. Lisa Feldman Barrett calls the whole process body budgeting, and interoception is how the budget is felt.

   Draft, to be replaced with my own words

3. Processing sensory data requires a lot of resources.

   It’s not just the work of gathering data from the world, but also the work of adding layers of context, meaning and memory to build it into a whole experience. Not just images and sounds, but emotions, significance and understanding too.

4. The mind builds those experiences in two ways:

   • Bottom-up processing: our body collects sensory data, and our mind adds layers of context, memory and significance to construct that data into something meaningful.
   • Top-down processing: our mind doesn’t wait for sensory information to arrive and then work out its significance. It predicts it, based on prior experience.

5. Top-down processing is cheap. Bottom-up processing is expensive.

   So when what we predict matches what we sense – close enough – the brain takes the cheap route, saving resources for what comes next.

6. Autistic people tend to rely more on high-cost, bottom-up (sensory) processing.

   Non-autistic thinkers tend to rely more on energy-saving, top-down (predictive) processing.

   Why? Here’s why I think monotropic theory explains this → Monotropism × Predictive Processing (thread coming soon)

7. Overwhelm is the feeling that tells you processing demands are about to exceed processing capacity.It’s an early alarm that warns you — not with words but with a feeling — that if you continue on this path in this way, you won’t have the processing resources you need to safely navigate the path ahead.

8. The mind instinctively responds with behaviors that protect you from more demands. You cover your ears, you run away, you snap “leave me alone,” or you hide.

   But the instinctive response to overwhelm doesn’t only happen in ways we can see. The nervous system activates to shift resources to where they’re needed and coordinate the response. The entire body, deep down to the cellular level, braces to conserve and prepare.

   Hey Dr. B! What does it mean that the body “braces”?

   When the brain predicts a demand it may not be able to meet, it treats it as a threat and mobilises. The sympathetic nervous system speeds the heart and breathing and tightens muscle; the adrenal glands release adrenaline and then cortisol; blood is shifted toward muscle and brain and away from digestion and repair. This is allostasis in action: resources moved to where the brain predicts they will be needed. Every part of it is paid for from the same budget, which is why bracing itself is a cost.

   Draft, to be replaced with my own words

   Short term, we were built for this. It’s how our mind and bodies keep us safe. But when the body braces for too long, the cells fall behind on their own upkeep. Waste that would normally be cleared builds up, and the immune system reads it as damage. Cue inflammation.

   Hey Dr. B! How does bracing for too long turn into inflammation?

   Cells run constant housekeeping: breaking down damaged proteins and worn-out mitochondria (autophagy), and in the brain, flushing the space between cells, mostly during sleep. These are low-priority, energy-hungry jobs, and under sustained stress they are among the first to be cut. Debris then accumulates. Fragments from stressed mitochondria look, to the immune system, like fragments from injured or infected cells, so it responds the way it would to an injury: inflammation. Bruce McEwen called the wear and tear of a stress response that never stands down allostatic load; the mitochondrial piece of that story is newer and still being worked out.

   Draft, to be replaced with my own words

   But inflammation is expensive. It drains the budget even faster, and the cycle continues.

9. Until the whole system pulls the emergency brake.

   Cue burnout.