Lessons 1 and 2 covered what an attack is. Here is why it escalates rather than just happening.

It starts with a sensation. Not necessarily an alarming one — a skipped beat, standing up too fast, coffee, heat, the tail end of a cold, a flight of stairs. Something in the ordinary noise of having a body.

Then the sensation gets read. Fast, wordlessly, before anything you’d call a thought: something is wrong. And that reading is itself a threat detection, so it fires the alarm — more adrenaline, stronger sensations. Which is more evidence that something is wrong.

What’s happening splits into two parts, and the split is useful because the two are fixed differently:⁴

• Interoceptive conditioning — ‘learned anxiety focused on internal states via aversive associations — such as learning to be anxious about elevated heart rate because of a previous association between elevated heart rate and a panic attack.’⁴ A plain association: this feeling, then that terror. It doesn’t need your agreement and it doesn’t respond to argument.
• Misappraisal — ‘misinterpretation of sensations as signs of imminent death, loss of control, and so forth.’⁴ The reading itself, which is available to examine, and which Unit 2 is about.

Two consequences follow, and they explain a lot.

The first: attacks can start before you notice anything. The evidence is explicit that ‘slight changes in relevant bodily functions that are not consciously recognized may elicit conditional anxiety or fear and panic due to previous pairings with panic.’⁴ The trigger can be below the threshold of noticing. So an attack that seems to come from nowhere isn’t evidence of anything sinister — it’s evidence that the cue was small.

The second is stranger, and it settles a question people find frightening: this conditioning can fire while you’re asleep. Nocturnal panic works ‘through a process of interoceptive conditioning, whereby low-level somatic sensations of arousal or anxiety become conditional stimuli’, and these responses ‘are not dependent on conscious awareness of triggering cues.’⁴ Waking in an attack does not mean it came from a nightmare or from something buried. It means the cue was physical and you were not awake to notice it.

There’s a third consequence, and it’s the one that shapes daily life. Once a sensation has become a cue, you start watching for it. That watching is not neutral: attention turned inward finds things. Bodies produce a steady stream of minor sensations that nobody normally notices — a flutter, a tightness, a moment of lightheadedness on standing — and monitoring reliably surfaces them.

So the vigilance meant to give you early warning ends up supplying the loop with material. That’s why the hours after an attack are the highest-risk hours for another one, and it’s what Lesson 2 meant about the long tail contributing to recurrence.

So where does this program break in? Not at the sensation — you can’t stop having a body. At the reading, and at the things you do afterwards. Those are the two reachable points on the loop, and they’re Units 2 and 3.