Issue 001 · 22 September 2026

The thing underneath the practices

I spent years looking for something I could not see, and kept walking past the thing that was doing the work.

For many years I have been exploring practices that most people would file under spirituality, or energy.

I have done a lot of meditation, including a Vipassana retreat, along with qigong, reiki, yoga, yin especially, and various other things filed under energy work or bodywork.

All of them are good, and that period of my life is what brought me to them. But I think I was looking for something energetic, something that could not be seen. And while I was looking for that, I was overlooking something we get taught about at school and then never think about again: our nervous system.

Every practice I have done, and still do, has an end goal. I think all of those goals run through the same place, which is a regulated nervous system. You do yoga to stretch, to get strong, to connect with yourself or with other people, to relax, to be more present. None of that happens if your nervous system is dysregulated. So I think that is the main point, not the side effect.

The following might sound like a strong statement. I do not think you can live a good life while your nervous system is dysregulated around the clock. I really do not think it is possible.

Dysregulation itself is part of being human. It happens, and being able to go there is healthy. Being stuck there is the problem. It drains you. It puts your energy into surviving something that is not in the room. And it makes it hard to enjoy what life actually is, never mind the small things.

So treat your nervous system as one of the most important things you have. Get to know it. Do not be afraid to feel it, which means not being afraid to feel your body. Give it the respect it deserves, and mostly that means giving it the rest it is asking for, from work, from people, from stress, or from plain physical tiredness.

New research this week

This week: what a sleep tracker actually does for insomnia, whether your heart rate variability score means anything day to day, an ear clip sold to calm the nervous system, what meditation does to the stress hormone, and whether cold water holds up.

  1. Stimulation and devices

    Sleep trackers helped people fall asleep about four minutes faster, and left their insomnia where it was

    Wristbands and rings are usually sold as a way to measure your sleep. This review asked a different question: if you use one as the treatment itself, do people with insomnia sleep better? Sixteen trials were combined. People fell asleep about four and a half minutes faster and said their sleep was slightly better. The questionnaire doctors use to decide whether someone has insomnia at all showed no change.

    What it means. A tracker can shift the numbers it measures without shifting how bad your insomnia is. If you have been wearing one for months and still sleep badly, the device is not failing you in some way you could fix by using it better.

    Worth knowing. The margin around those four and a half minutes includes zero, so the next trial could find nothing. The researchers say it plainly: a cheap addition, not a replacement for the therapy that works.

    Sixteen trials combinedn=910
    Read the study →
  2. Measurement

    Your heart rate variability says something about you in general, and almost nothing about today

    Heart rate variability is the small difference in timing between one heartbeat and the next, and wearables sell it as a daily readiness score. The question here was whether last night's number predicts how you will feel today. Fourteen people wore a Fitbit for about a month and rated their energy and tiredness every day. People who ran higher variability in general were less tired in general. But within any one person, one night's number told you almost nothing about the next day. How long they had slept did.

    What it means. The daily score on your ring or watch is describing you as a person, not your Tuesday. A low reading on a given morning is weaker information than how long you actually slept, which the same device already tells you.

    Worth knowing. Only fourteen people, and nobody was assigned to anything, so this shows what goes together rather than what causes what.

    Fourteen people tracked for about a month eachn=14
    Read the study →
  3. Mind and attention

    Mindfulness training lowered the stress hormone, and a third of the effect was being in a programme at all

    Cortisol is the hormone the body releases under sustained stress, and it is the usual way of measuring stress physically rather than by asking. Researchers pooled thirty-nine studies of the standard eight-week mindfulness course, covering just over two thousand people. Cortisol came down. But the size depended on what the course was compared against: against doing nothing the effect was noticeably larger than against doing some other structured activity.

    What it means. Some of what mindfulness does is mindfulness, and some of it is having somewhere to be each week with other people doing the same thing. That is not a debunking. It does mean the structure is part of the active ingredient, which is worth knowing if you have ever tried to get the same result from an app alone.

    Worth knowing. Cortisol is a proxy. A measurable drop in a hormone is not the same as feeling less stressed, and the review does not report whether the two moved together. The authors also say the variation between studies is large and they cannot explain it.

    Thirty-nine studies combinedn=2,059abstract only
    Read the study →
  4. Environment and inputs

    A review in a major psychiatry journal calls cold exposure promising and still unproven

    Cold plunging is sold hard for mood, anxiety and stress. This review went through the trials and the three biological routes by which cold is supposed to work: the adrenaline system, the body's main stress-hormone axis, and inflammation. It found real signals on short-term mood, and no settled account of why. It also found that the psychological improvements people report have not reliably lined up with any measured biological change.

    What it means. Feeling better after cold water is well documented. The mechanism everyone cites for it is not. If you get something out of it, that is not invalidated by this; but claims about what it is doing to your nervous system are running ahead of what anyone has shown.

    Worth knowing. The review's sharpest point is about who volunteers: people who sign up for cold-water studies are already people who do things for their health, so part of any comparison is between them and everyone else.

    Review of trials and mechanismsabstract only
    Read the study →
  5. Stimulation and devices

    An ear clip lowered how much pain people reported after surgery, but not how much painkiller they took

    The ear is one of the few places where a branch of the vagus nerve comes close enough to the skin to be reached from outside, which is why small clip-on stimulators are sold to calm the nervous system. Researchers collected every trial that had compared a real device against a convincing fake, seven in all, and combined them. People wearing the real one said they were in less pain and asked for extra relief less often. The amount of painkiller they actually took was no different.

    What it means. This is the best-controlled evidence going for the ear devices, because every trial used a convincing fake. What it shows is a change in what people report and not in what they do, which is the gap worth holding on to when one of these is sold to you for stress.

    Worth knowing. The difference in reported pain was under one point on a ten-point scale, which is less than people usually notice. All seven trials came from one country, and the researchers rate their own evidence as weak.

    Seven trials combinedn=684
    Read the study →

Every card links to the paper it describes. Where a study was read from its abstract only, the card says so.

One issue a week

New research on the nervous system, explained plainly, with an essay beside it. Sent once a week. Nothing else, ever.

Educational, not medical advice. This site reports what research shows; it cannot tell you what to do about your own health. If you are in distress or your symptoms worry you, contact a qualified professional.