Why sleep gets worse when the clocks go back

The clocks go back on 25 October, and most people brace for the wrong thing. The hour is not the problem. The hour is a one-off nudge that sorts itself out within a few days.

What follows it is the part that actually changes how you sleep, and it lasts until spring.

The real change is light
From late October onwards, the amount of daylight reaching you collapses. Not only because the days are shorter, but because the hours that remain are the ones you spend indoors.

That distinction matters more than it sounds, because indoors is dimmer than it feels. Your eyes adjust and the room looks fine, while the signal reaching the body clock is a fraction of what it would get outside on an overcast morning. Through winter, a lot of people get almost no properly bright light at all.

The body clock runs on that signal. Strip it out and the clock does not stop. It drifts.

What the research shows
The clearest demonstration comes from taking people out of the modern lighting environment entirely.

A 2013 study put participants through a week of camping with no electric light, torches or phones. Exposure to natural light alone pulled the internal clock into line with solar time, so that biological night began near sunset and ended near sunrise. Back in the constructed environment, with less daylight by day and more light after dark, circadian timing sat measurably later [1].

The same group then repeated it across seasons. After a week in a natural winter light-dark cycle, biological night and sleep both began earlier than in the modern lighting environment. They also found that the biological night expands in winter compared with summer, as it does in other animals, and that in the modern environment the clock sits later than it should in both seasons [2].

That is the mechanism in one sentence. Your biology is set up to run a longer night in winter, and modern indoor life withholds the signal that would organise it.

Why it feels like bad sleep
A clock running late is not experienced as a clock problem. It is experienced as lying awake, then waking up tired.

The internal night starts later than it should, but the alarm does not move. You lose sleep off the front end, take it off the back, and spend the winter feeling as though something is wrong with your sleep when the timing is what has shifted.

What actually fixes it
Light. Specifically, getting outside early in the day, and being stricter about dim evenings than you would be in June.

It is worth saying how effective that is, because it is free and we would rather you did it than bought something. In the seasons study, a single weekend spent in natural light achieved around 69% of the circadian shift the researchers had previously measured after a full week [2]. Two mornings outdoors does most of the work of seven.

Ten to twenty minutes outside shortly after waking, without sunglasses, on an ordinary grey morning, beats anything in a bottle for this particular problem. If your sleep problem is a timing problem, daylight is the intervention and nothing we sell competes with it.

Where a patch does and does not help
This is also the clearest illustration of why Sleep Deep contains no melatonin.

Melatonin is a timing signal. It tells the body what hour it is, which is precisely the function daylight performs better, earlier in the day, at no cost and without the dose problems we have written about before. Using a supplement to shout the time at a clock that is short of light is treating the symptom with a worse version of the thing it is missing.

What a patch can do is the other half of the problem. Getting the timing right does not help much if arousal stays high once you are in bed, and that is a different system. Sleep Deep works on GABA-A, the brain's main inhibitory pathway, through honokiol, apigenin, PEA and oleamide. None of those tell the body what time it is. They support the process of settling once it is time.

So the honest order is this. Fix the light first, because it is free and it addresses the cause. Then, if falling and staying asleep is still the issue, that is where a formulation has something to offer.