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Somnambulism analgesia

By Timothy Cocks Science and the world 19 Nov 2015

I’ve asked the question whether it is possible to feel pain while asleep before. It led to some great discussion, as well as a fascinating first hand report. A recent paper in Sleep (I love these simple, unambiguous journal titles) reported on an experiment that asked known somnambulists about their experiences of pain. A press release from the American Academy of Sleep Medicine detailed some intriguing results:

Sleepwalkers feel no pain, remain asleep despite suffering injuries

“Among sleepwalkers with at least one previous sleepwalking episode that involved an injury, 79 percent perceived no pain during the episode, allowing them to remain asleep despite hurting themselves.

“Our most surprising result was the lack of pain perception during the sleepwalking episodes,”… “We report here, for the first time, an analgesia phenomenon associated with sleepwalking.”

…one patient sustained severe fractures after jumping out of a third-floor window while sleepwalking but didn’t feel the pain until after waking up later in the night. Another patient broke his leg during a sleepwalking episode in which he climbed onto the roof of his house and fell down, but he didn’t wake up until morning.”

The phenomenon we collectively call ‘sleep’ actually represents a range of altered states of consciousness – in some we can have terrifying experiences while being paralysed, and yet in others we can behave and function at high levels (jump out of windows and climb on to roofs) but not experience pain despite serious injury – and quite possibly not have any subjective experience at all. This is what makes the question of pain while sleeping so captivating to me – it provides a tantalising glimpse into the issues at the very heart of pain – consciousness and subjective experience.

-Tim Cocks


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  1. rsser

    In a waking state, can one fully feel two pains at once?

    I’m not sure I can.

  2. Tim, I know that I often wake with headaches (specially after NOI functions). I am aware that I have a headache if I am in a light sleep, but then I goings a deeper sleep. If pain is an output of the brain, surely what wakes me is the biological reason for the pain that I will experience when I awake… Or In that semi-conscious state just before I do so. Is waking part of the early warning system – “. Wake NOW and take Panadol”

    1. If I may come in here and offer an answer…

      — You can feel pain in REM sleep, because there is a remnant of self-consciousness. ie. there’s a ‘you’ operating as you do your dream activities..

      — You might feel some sort of pain in NREM sleep, but it will certainly be much less.

      — You cannot experience pain in slow wave sleep, a subset of NREM. The reason is that there is no self-consciousness in SWS.

      Cruelly, people with persistent pain often have significantly less ability to drop into SWS. Read here:

      I also wrote something on this in the thread ‘self matters’. But it’s not accepted by experts.

  3. Yep, thought so although I didn’t have the science. Intersting about lack of SWS sleep for persistent pain sufferers

  4. Perhaps a funny thing about pain and sleep is that people just don’t remember their ‘painless’ sleep. Only the disturbed pain affected sleep (half-sleep !) is etched into memory because of the ‘conscious scars’ that are created whilst it’s occurring. The ‘painless’ sleep goes unrecorded because it occurred in a non-conscious state, and has no requirement to be consciously recorded.

    The question that arises for me on this matter, and repeats itself over and over, is this…’Is there any requirement for pain sensations in deep sleep (SMS or non-rem sleep) ?’ If the answer appears to be ……’There seems to be no requirement’, then that puts a definition on pain as a ‘conscious only’ event. That, subsequently arouses the question…..’If so, why is pain only relevant to the conscious state, because such a relationship suggests a purpose to ‘pain’s’ conscious only relevance ?’.

    The excellent article above approaches the possibility of these questions, tentatively. What I think is needed is an effort to rise above the temptation to always use our conscious perceptive prism as our guide. If we could conceptualise as though we were perceiving the sleep/pain event from the non-conscious perspective, I (consciously) think the relationships between sleep, pain, and conscious relevance, might assume a more definable clarity. How to rise above a conscious appreciation is probably the key to unlocking a logical rationale which has its own momentum. It might seem, in fact, that there are inherent conscious restrictions which discourage us from attempting such ‘unbound by conscious rules’ perceptions. Perhaps different rules apply in the non-conscious state. One issue which reflects on all this is the fact that the autonomic systems continue functioning regardless of what state we’re in, and that points to the possibility that consciousness does not have access to our most necessary survival tools….perhaps for good reason !

  5. ” In a waking state, can one fully feel two pains at once? ”

    That’s a really interesting question. Dr Patrick Wall did a BBC Radio science discussion on this very topic back around 2004…unfortunately I don’t have a link to it, but I’m sure it’s available somewhere. It’s probably not too relevant to the sleep/pain issue, except in one respect….perhaps.

    Consider a patient with a common toothache and a common earache occurring at the same time, with equal perception of pain intensity. It would seem that, whichever complaint is being consciously focused on, at any given time, is the one which registers the dominant pain perception being experienced…at that given time. It might also seem that, simultaneously, the pain from the other complaint disappears momentarily. That , if so, obviously points to pain, perhaps, only being relevant to the limited conscious ability to only focus on one issue at a time….to the exclusion of the relevance of the ignored complaint not having a requirement to interfere with that singular focus in any way. Thus, the temporary non-requirement of a pain perception for the ignored complaint seemingly allows for this phenomenon to occur over a vast range of patients and conditions. It looks like a non-conscious prioritising hierarchy is having a say there. The relevance to the sleep/pain issue lies in the ‘requirement’ issue, where , even in the conscious state, a second complaint can be temporarily ignored ( rendered non-conscious ), and pain perceptions are not required.

    When I was growing up, we had a saying when anyone banged their knee accidentally and ‘yelped’…..we would say….’ Bang the other one and you won’t feel the first knee !’ I’m beginning to see the resonance !

    1. rsser

      Zaccly. I just got an unwanted demo of this when cracked rib pain displaced regular lower back pain – while the signs of the back problem remained.

      I’ve tried a test by pushing two finger nails hard into my skin at different points. Seems I can only apprehend one pain at a time.

      Just a bit more evidence of pain being a construct.

      1. I would see that more as evidence of pain being an adaptable tool, rather than a ‘construct’….but maybe the meaning is similar. Any self-testing, which is fabricated, is unlikely to reveal anything relevant. The threat must be ‘real’ and recognised as such by the autonomic response systems, otherwise the resulting observations can’t be trusted to not be ‘confirmation biased’….no matter how serious the imposed threat.
        Think of it like this….our autonomic response systems are ‘aware’ of any consciously induced actions, and will only respond with usual measures if the threat is considered ‘real’ or ‘not consciously fabricated’. If the threat is considered to be ‘consciously fabricated’, then the autonomic systems will attempt to discourage that threat source initially, probably with an increased pain perception, before applying themselves to any damage resulting from the threat.
        That’s speculative, of course, but for me, it would make sense for any functionality to have a rational premise such as that described.

  6. I’d be more inclined to perceive pain evolving from such a scenario as an adaptable utility, rather than as a conscious construct. But, perhaps, a similar meaning is intended. I also don’t think that any self-testing would be relevant, if only for the simple reason that the autonomic systems are unlikely to react to an obvious conscious fabrication of threat, as they might do to a ‘real’ threat of injury. Too much confirmation bias going on as well. Unfortunately, the only method of assessing credibility for the ‘ 2 pains at once ‘ phenomenon might be by means of a blinded survey of the narratives of a suitable demographic experiencing it. There are just too many pitfalls with self-testing to warrant any scientific credibility. However, that doesn’t exclude anyone from studying their own experiences, and drawing a conclusion from them. That’s valid….but only to that person.

  7. Perhaps this discussion has drifted somewhat from the intention of Tim’s article which raises some important issues about the relationships between injury and pain in the ‘somnambulist’ state. If validated, the findings reported suggest that sleepwalkers who are injured, whilst sleepwalking, feel no pain until they next awaken ( become conscious again ). There are implications pertinent to our definitions of pain which are aroused by such events. Obviously it’s quite difficult to monitor somnambulism to validate the findings over a wider scale, because of the unpredictable nature of the event. We’re probably still not quite sure what exactly somnambulism is , in relation to what we perceive as normal behaviour….is it a malfunction or misbehaviour ?, or is it the non-conscious temporarily assuming a ‘mimicked’ conscious role ?….those questions are still unanswered, far as I know.
    Personally, I think we can discount malfunction or misbehaviour, because of the commonality, consistency, and widespread recording of the sleepwalking event. Also, without defining what the normal functioning of sleepwalking should be, we really can’t reasonably move on to suggesting it might just be a malfunction or misbehaviour. So I’d be more inclined towards some kind of non-conscious ‘mimicking of consciousness’ event, perhaps akin to dreaming….almost as though a temporary state of conscious/non-conscious crossover has been triggered somehow. Why this should happen asks its own questions about the nature of both states, and I’m sure that’s still being researched for some clarified definition.
    The question of the seeming non-registering of pain during sleepwalking event, until the subject awakens, is very interesting…..considering that a person who is in deep sleep, and not feeling the pain of an ongoing injury ( broken arm, for instance ) can be woken by a mere pinprick to a toe. That is a conundrum in itself, indicating some non-conscious ignoring of a current injury whilst still being alert to a ‘new threat’ of relative minor significance. There are resonances in that comparison of normal deep sleep and sleepwalking, perhaps in regard to a non-requirement for pain sensations in both states, but with the exception of the seeming negation of the ‘always alert’ status when sleepwalking only.

    Food for further thought, no doubt….and glad to see the matter opened for discussion.

  8. “considering that a person who is in deep sleep, and not feeling the pain of an ongoing injury ( broken arm, for instance ) can be woken by a mere pinprick to a toe”.

    What do you base this on, Gerry? People in SWS are almost impossible to rouse, even with painful stimuli or gross movements.

    But otherwise I agree, the commonly used definition that pain represents a ‘threat to the body’ is not accurate. Pain is a threat to self-image.

  9. ” Gerry? People in SWS are almost impossible to rouse, even with painful stimuli or gross movements. ”

    My opinion on that is based mostly on personal experience. To add balance to that, I would say that my experience of assessing the usual research into sleep states is that the research often comes with a pre-agenda, designed to only focus on expected pre-determined outcomes. Quite often, the detail of what is really happening is overlooked , possibly in favour of assumptions that have been fabricated before the research even takes place. There’s an obvious blind spot to such investigations….and the need to approach the issue from a broader perspective doesn’t make itself obvious.

    There are many levels and phases of the deep sleep state, probably dependent on individual physiology and experience. I don’t think there’s any confirmation that it is exactly the same for everyone. There’s ‘falling into deep sleep’, there’s ‘waking from deep sleep’, there are ‘half-sleep’ phases, there’s ‘disturbed’ deep sleep etc. Any of these states will have their own requirement for pain sensations to register, if at all. Perhaps the only consistent factor is that full deep sleep guarantees a pain free experience….and that might seem to point to a non-requirement for pain in that state. However, it seems that a certain level of autonomic alertness is maintained, which has the ability to awaken if a new threat occurs, even if that threat is minor in comparison to an ongoing painful injury which isn’t registering its usual pain in the deep sleep state. Pain, from either threat, only begins to register with the waking process. Once awake, the pain from each threat will assume their own status of importance, depending on level of threat. So, even though there is pain-free sleep for a serious threat, a new minor threat will cause wakefulness, and then both pains will register and be consciously assessed. I can’t prove that, but it seems to be what really happens.

    For me, it would all seem to be predicated on an autonomic need, or requirement, for pain …..and that , in itself, would depend on a need for consciousness, only, to feel the restraining sensations of pain. The ‘somnambulist’ tests would seem to confirm this….where pain only becomes evident on waking. It’s actually quite difficult to overview all this from the ‘conscious’ perspective, because consciousness is only a ‘part player’ in the whole event, and other perspectives get lost in the conscious fog which is restrained by a conscious agenda. The bigger picture might suggest that pain is a utility employed by the autonomic protective systems, which actually adds to conscious confusion ….for the perfectly good reason that consciousness needs to have its ability to intervene inappropriately in any threat restrained.

    That would be my observations in a nutshell, but of course, without proper focused investigation, it’s only speculative.

    Re….”pain represents a ‘threat to the body”……I’d agree that this is a lazy option for putting a definition on pain. However, I don’t of its purpose as being a threat to ‘self-image’ only. I’m more inclined towards an autonomic requirement for pain in the conscious state, which can be relaxed in certain sleep, or unconscious, states.

  10. Pain is a threat to self-image

    I’ve been puzzling over that comment for a few days……got me thinking about pain’s attributes, in terms of its relationship with consciousness. Generally speaking, I don’t think there is any doubt about pain not being a ‘wanted’ or ‘desired ‘ attribute in anybody’s subjective sense of consciousness or self-awareness. Any notion that any person, particularly chronic pain patients for purposes here, might be complicit in desiring such an ‘alien’ attribute as pain, and allowing it to dominate their everyday conscious existence, seems counter-intuitive to me. I’m aware of Munchausen syndrome, self-mutilation syndrome etc but I think these are minority exceptions to the rule, and they may well be less ‘desire’, and more ‘self delusional’ in nature. Pain experiences are, generally, and by a huge majority, unwanted…..and that’s the consistent standard we must work around when trying to establish definitions which are likely to resonate with the subjective experience of pain. Making an exception for possible complicity in chronic pain narratives is, I think, an assumption too far, and probably unproven.

    ” Pain as a threat to self-image “, could be seen in another way. No-one would want their normal conscious clarity disturbed, or dominated, by pain perceptions……and that’s exactly the effect of any pain experience, whether chronic or not. I think we all realise how that affects how we present ourselves to others, and we are all possibly aware that , in doing so, we are displaying a self-image which is likely to be rejected, or at least questioned or ignored. Seldom is the entire complexity of a pain experience fully accepted for what it is. Empathy, and resistence, issues play themselves out on that scenario, all the time. However, the route to proper treatments requires good understanding, and so there’s really no avoiding someone, in pain, having to engage with others on that unwanted level. This, maybe, is where a ‘threat to self-image’ enters the equation, and subjective narratives can be consciously altered to avoid any over-sensitised vulnerabilities. Enticing somebody else into a fuller understanding of a pain experience, is not a morale booster, in any sense, and it comes with a sense of ‘lowering the tone’ in any encounter.

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