Brave subjects shocked a lot for science: habituation and sensitization

If you keep getting stung, do you get used to it? This is called “habituation” in the world of pain science.

Or does it just keep getting worse? “Sensitization.”

“It depends,” but on what? Who habituates, who sensitizes? Answering this question was the goal of a new “torture” study by van der Miesen. Another post about “zapping,” but this time the shocks weren’t for therapy — they were for science.

van der Miesen MM, Vossen CJ, Eck J, et al. Assessing the reliability and association of pain ratings and skin conductance responses: Insights from habituation and sensitization to pain. J Pain. 2025 Sep;37:105557. PubMed 40945640 ❐

If you were lightly zapped over and over again, would you habituate? Or sensitize?

Fifty-four healthy young adults endured many mild electrical shocks for about an hour — uncomfortable but manageable (their anxiety was middlin’). The shocks came in three batches of 25 shocks spaced about 20 seconds apart, and there was a little rest between batches.

On average, these zapees habituated — but often not at first. Many participants sensitized initially.

Sensitization was more “predictable” (higher test-retest reliability), possibly suggesting a more trait-like pattern — something about that person at any time, not just that day, or that hour. Maybe even a neural rigidity that predisposes some individuals to chronic pain.

They also measured “skin conductance response,” AKA how much is this making you sweat? Actual visible sweat not required, though: microscopically moist skin is an inevitable sign of the autonomic arousal (stress response) that often comes with pain. But in this study, SCRs declined — even as pain ramped up. The stress response generally declines with repeated, identical stimuli, probably thanks to steadily declining perception of threat — “Oh, is that all? Nothing worse? No big deal, I got this!” But that happened without also easing pain. So the increasing perception of safety was calming — the pain “means” less, becomes less stressful, a function of the mind — but it was not also obviously analgesic.

Anxiety, fear, and positive self-talk had little to do with these patterns. Fear of pain was only weakly tied to sensitization early on.

Anything useful here?

It’s mostly just interesting. Mild, predictable shocks in calm, healthy volunteers aren’t much like the messy, scary pains of life. With more intense and chaotic noxious stimuli, both pain and stress would likely stay high — but we’ll never get ethics approval for that study.

It’s lovely to think that we might be able to prevent or ease chronic pain by promoting habituation and minimize sensitization somehow … but we don’t really know how to do that … and this study isn’t encouraging about some of the most obvious possibilities.

On the other hand, it is at least nice to know that habituation is possible. Nothing wrong with shooting for it!

Update: a bit more about the “practicality” of this science

The “ink” wasn’t even dry before I was getting comments like, “Useless!" and "Who cares!” and “100% irrelevant to anything a person might actually suffer.”

I know, I know, it’s far from “useful.” But I wouldn’t be doing my job if I didn’t report on at least some of this stuff … if for no other reason to to discuss why it matters or does not matter.

But clearly not all bio-science can or even should have obvious practical value or clinical relevance. We can probably easily agree that this study is >98% clinically useless, but the abstract value … that’s much messier. Even if it never changes patient care directly, this kind of work deepens the map of pain itself. You can’t treat what you don’t understand, and understanding requires probing the fundamentals: how perception adapts, what’s trait versus state, how physiology and experience diverge. There’s the potential for better models and clearer thinking about why some people recover while others don’t. It’s basic research, building a scaffolding of knowledge for other work to build on.

So yes, sometimes I report on a study that has little or no obvious value to patients or clinicians.