What happens in the body

In this chapter

1. What has been measured
2. What is assumed without having been measured
3. Subspace
4. Topspace and flow
5. What this changes for safety
6. Drop
7. Aftercare in practice
8. Further reading

There are few studies on the physiology of BDSM, and they are small. This chapter separates what has been measured, and in how many people, from what gets repeated without evidence.

What has been measured

A few teams have done something that sounds simple: take saliva or blood samples before and after a real session (a “scene”, in the community’s vocabulary) between consenting partners, and compare them.

Cortisol

Cortisol, the stress hormone, rises in the person who is tied up, receiving or obeying. Sagarin and colleagues measured it in the saliva of 58 practitioners, across two studies; in the person doing the acting, it does not change¹. Wuyts’s team found the same rise in submissives, in 35 couples compared with 27 controls, but not in dominants².

One detail in Sagarin’s work matters: when the scene went well, cortisol then comes back down and the feeling of closeness between partners increases¹.

Endocannabinoids

Endocannabinoids are molecules made by the body, linked to pleasure, reward and the regulation of pain³. In the submissives of the Flemish study, they rise after the session, and one of them (2-AG) is higher when the scene includes pain. In dominants, they rise when the scene is built on power play rather than on pain². In submissives, the rise in cortisol and the rise in endocannabinoids go together⁴.

Pain threshold

In the same couples (34 dominants, 33 submissives and 24 controls included in the analysis), practitioners have on average a higher pain threshold than controls, and that of submissives rises further, temporarily, after the session⁵.

Testosterone

The results contradict each other. Sagarin observed a rise in women in the bottom role, the one receiving¹; the 2022 systematic review, which brings together the ten available publications on the biology of BDSM, considers its role unclear³.

Brain imaging

Imaging studies are not about sessions. They compare people who are or are not interested in BDSM, for example while they look at pictures. They suggest a role for the ventral striatum and the parietal operculum (pleasure, reward), the somatosensory cortex (pain perception) and the anterior insula (empathy)³.

Attention

Ambler and colleagues randomly assigned 14 experienced practitioners to the role of top, the one acting, or of bottom, the one receiving. After the scene, bottoms did less well on an attention test (the Stroop test), which is consistent with “transient hypofrontality”, a partial standby of the prefrontal cortex. Tops, for their part, described a state of “flow”⁶.

What is assumed without having been measured

You read everywhere that BDSM triggers an “endorphin rush”. That is plausible, not proven. The only known session study that measured beta-endorphins, in the blood, reports effects in its abstract only for cortisol and endocannabinoids². What happens in the brain has never been measured during a session. Adrenaline and dopamine were not measured in the session studies. The 2022 review mentions oxytocin, a hormone associated with attachment, but considers its role less clear than that of cortisol or endocannabinoids³.

The most useful analogy comes from running. The runner’s high was long put down to endorphins. In mice, Fuss and colleagues showed that the calming effect and the reduced pain after running depend on cannabinoid receptors; the euphoria itself cannot be studied in animals⁷. In humans, Boecker and his team observed with imaging (PET), in 10 athletes after two hours of running, that the brain releases opioids in prefrontal and limbic areas, in connection with the euphoria they felt⁸. So both systems play a part. BDSM at least shows changes in endocannabinoids, which makes the parallel tempting. It remains a parallel.

One phenomenon, however, is established: stress-induced analgesia. Acute stress dampens pain, through several pathways, including the opioids and cannabinoids the body produces⁹.

Subspace

Many bottoms describe a state of its own during an intense scene: a floating head, time stretching out, pain far away, words that are hard to find. It is called subspace.

The best-supported hypothesis combines three mechanisms. Analgesia (endocannabinoids, probably opioids). Strong activation followed by release (cortisol, most likely adrenaline). And a partial standby of the prefrontal cortex, the area that plans and judges. Each piece rests on a measurement or a known phenomenon; the whole has never been measured as such: nobody has tracked a subspace live, and the attention study involved 14 people⁶.

Context matters as much as chemistry. The same stimulation does not have the same effect depending on trust, how safe you feel, the sense of choosing, the bond with the person in front of you¹⁰. In Sagarin’s work, the fall in stress and the growing closeness only appear if the scene went well¹. A slap negotiated with someone you trust and the same slap in a moment of doubt are not the same experience, neither for the mind nor, probably, for the body.

Topspace and flow

On the top’s side, Ambler measured a state close to the flow described by the psychologist Mihály Csíkszentmihályi: absorption, narrowed attention, time flying by⁶. Many call it topspace. Flow helps you be precise. It has a possible downside: attention tightly focused on one movement can miss what is happening elsewhere, a hand turning pale, a change in breathing.

What this changes for safety

Put the above together: in this state, you feel pain less and judge less well. Pain, which serves as an alarm, warns you later. And a safeword requires you to notice that you need to stop, then to find the word and say it. That is exactly what becomes difficult when attention is dulled.

In practice, for the top:

• check in regularly with questions that need more than a yes: “give me a number from 1 to 5”, “squeeze my hand twice”;
• look at what does not lie: breathing, skin colour, how quickly they answer, how warm their hands and feet are (for rope, see Rope);
• when answers become slow or vague, lower the intensity or stop: subspace is not a goal to reach at any cost;
• agree in advance on a signal that does not rely on speech (see Consent).

Drop

After a scene, some people feel a low: tiredness, sadness, anxiety, guilt, sometimes for no obvious reason. This is called sub drop, and top drop when it affects the person who led (see drop). Sprott and Randall distinguish an immediate drop, in the minutes that follow, from a delayed drop, a few days later, sometimes up to a week later¹¹.

The most widespread explanation is a hormonal comedown. It has never been tested. The same authors point out that the hormonal changes put forward play out over minutes, not days, and they propose psychological explanations for delayed drop¹¹. So we do not know what causes it. We know that it exists, and that it affects both roles.

Aftercare in practice

Aftercare is the care that follows a scene. It is negotiated beforehand, like everything else, because everyone has their own needs: some want to be held, others want a glass of water and ten minutes of silence. The principle is nothing specific to BDSM: after any intimate moment that was a little intense, a gentle moment together and a message the next day do you good.

For the person who received:

• warmth (a blanket is enough), water, something to eat;
• a look at the skin, the marks, circulation, the joints;
• contact if they want it, words or silence depending on what they prefer;
• no driving and no important decisions until they have come back down.

For the person who led:

• they too may need to hear that everything was fine, and to talk about what they did;
• drinking, eating, sitting down: top aftercare is not a luxury.

The next day, check in. A message is enough: “How are you feeling today? Did anything bother you?” Do it again a few days later, since drop can come late¹¹. If the low lasts, or if dark thoughts appear, talk to someone you trust or to a professional (see Resources).

Further reading

• Safety: the risks specific to each practice and the signs that mean you should stop.
• Consent: negotiating and choosing your signals.
• What the research says: well-being, personality and the limits of the studies.
• Tonight: take stock of how you are on the day before a session, aftercare included.

Sources

1. Sagarin, B. J., Cutler, B., Cutler, N., Lawler-Sagarin, K. A. and Matuszewich, L., 2009. Hormonal changes and couple bonding in consensual sadomasochistic activity. Archives of Sexual Behavior, 38(2), 186-200. link ↑↑↑↑

2. Wuyts, E., De Neef, N., Coppens, V., Fransen, E., Schellens, E., Van Der Pol, M. and Morrens, M., 2020. Between Pleasure and Pain: A Pilot Study on the Biological Mechanisms Associated With BDSM Interactions in Dominants and Submissives. The Journal of Sexual Medicine, 17(4), 784-792. The abstract states that beta-endorphins were measured. link ↑↑↑

3. Wuyts, E. and Morrens, M., 2022. The Biology of BDSM: A Systematic Review. The Journal of Sexual Medicine, 19(1), 144-157. link ↑↑↑↑

4. Wuyts, E., 2022. BDSM: pathological or healthy expression of intimacy? European Psychiatry, 65(S1), S805-S806. link ↑

5. Wuyts, E., De Neef, N., Coppens, V., Schuerwegen, A., de Zeeuw-Jans, I., Van Der Pol, M. and Morrens, M., 2021. Beyond Pain: A Study on the Variance of Pain Thresholds Within BDSM Interactions in Dominants and Submissives. The Journal of Sexual Medicine, 18(3), 556-564. link ↑

6. Ambler, J. K., Lee, E. M., Klement, K. R., Loewald, T., Comber, E. M., Hanson, S. A., Cutler, B., Cutler, N. and Sagarin, B. J., 2017. Consensual BDSM facilitates role-specific altered states of consciousness: A preliminary study. Psychology of Consciousness: Theory, Research, and Practice, 4(1), 75-91. link ↑↑↑

7. Fuss, J., Steinle, J., Bindila, L., Auer, M. K., Kirchherr, H., Lutz, B. and Gass, P., 2015. A runner’s high depends on cannabinoid receptors in mice. Proceedings of the National Academy of Sciences, 112(42), 13105-13108. link ↑

8. Boecker, H., Sprenger, T., Spilker, M. E., Henriksen, G., Koppenhoefer, M., Wagner, K. J., Valet, M., Berthele, A. and Tolle, T. R., 2008. The runner’s high: opioidergic mechanisms in the human brain. Cerebral Cortex, 18(11), 2523-2531. link ↑

9. Butler, R. K. and Finn, D. P., 2009. Stress-induced analgesia. Progress in Neurobiology, 88(3), 184-202. link ↑

10. Dunkley, C. R., Henshaw, C. D., Henshaw, S. K. and Brotto, L. A., 2020. Physical Pain as Pleasure: A Theoretical Perspective. The Journal of Sex Research, 57(4), 421-437. link ↑

11. Sprott, R. and Randall, A., 2016. Black and blues: Sub drop, top drop, event drop and scene drop. Journal of Positive Sexuality, 2(3), 53-61. link ↑↑↑