Twice a year the same thing happens: on the Sunday of the change everyone talks about the hour gained or lost, and by Tuesday some people have forgotten all about it while others have spent two days foggy, irritable and not quite sure why. It is neither imagination nor lack of willpower. One hour on the clock does not weigh the same in every body.
I have spent more than ten years researching the body clock and its relationship with mental health at the University of Málaga. Here is what happens, why it depends on your chronotype and what you can do this week.
Your body does not change the time: the clock does
Inside you there is a clock that sets when you get sleepy, when you wake up, when you are hungry and when you perform best. That clock resets every day, mainly through light. On the Sunday of the change the clock on the wall jumps an hour in one go; yours does not. It needs a few days to catch up, and in the meantime you live with a small lag, as after a short flight.
The October change is the gentler of the two: clocks go back an hour and most people sleep a little longer that night. The March one, which takes an hour away, usually costs more. But even the October change moves the light around: dawn comes earlier and dusk much earlier, and the internal clock notices that too.
Why some people are affected more
This is where chronotype comes in: the time of day your body prefers to work. There are morning types (larks), evening types (owls) and a majority in between. I have written about it in Owls and larks.
Chronotype is not entirely fixed. Age moves it (we are more nocturnal around twenty and earlier risers later on) and so does the season: in studies measuring the same people in different months, preference shifts slightly towards the morning from December to June. In other words, your clock is already adjusting by itself to the light of each season, and the clock change adds a sudden push on top.
Those who struggle most are usually the people who were already out of step before the change. And that has a name.
Social jet lag: the clock change that happens every week
In 2006, Till Roenneberg's team in Munich named something many people live with without knowing it: social jet lag. It is the gap between the hours you would sleep if nobody set your schedule and the hours imposed by work, school or your shift. Anyone who uses an alarm on weekdays and sleeps two hours longer at weekends is, in practice, crossing time zones every Monday.
It is not unusual. In a sample of more than 64,000 people, around a third carried two hours or more of social jet lag. And evening types carry the most, because almost every schedule is designed for early risers.
That is why the clock change is a good excuse to take a look at yourself: if a single hour knocks you off balance for a week, your clock and your schedule have probably been pulling in different directions for a while.
And what does mood have to do with it?
In our research we have found, time and again, that evening types score somewhat lower on variables such as emotion regulation, resilience, self-esteem and life satisfaction. Other groups have found that social jet lag is associated with more depressive symptoms.
These are small, statistical relationships, not destinies. That two things travel together across thousands of people does not mean one causes the other, nor does it say anything about you in particular. What they do suggest is that months of sleeping out of step leave you with less room to absorb whatever comes. The clock change will not make you depressed; but if you were already running on empty, you will feel it that week.
What to do this week
Morning light. It is what actually sets the clock. Getting outside for a while first thing, even when it is cloudy, helps more than any supplement.
Regular hours, weekends included. Getting up at a similar time every day does more for your mood than catching up on sleep on Sunday. Sleeping until two on Saturday is exactly what stretches the lag.
Less bright screen late at night. With darkness falling earlier, the temptation is to stretch the evening with your phone. Bright light at night pushes the clock in the opposite direction to the one you need.
Patience with yourself. A few days of tiredness or irritability after the change are normal. There is no need to turn them into a problem.
When it is no longer the clock change
If after two or three weeks you are still sleeping badly, waking in the small hours with your mind racing, or the low mood does not lift as the days settle, that is no longer the clock on the wall. It is worth talking it over with a professional.
If that is your case, we can talk for ten minutes on the phone first and see whether it makes sense to work together. With no commitment.
The studies I mention
- Wittmann, M., Dinich, J., Merrow, M. & Roenneberg, T. (2006). Social jetlag: Misalignment of biological and social time. Chronobiology International, 23(1–2), 497–509.
- Roenneberg, T., Allebrandt, K. V., Merrow, M. & Vetter, C. (2012). Social jetlag and obesity. Current Biology, 22(10), 939–943.
- Roenneberg, T. et al. (2004). A marker for the end of adolescence. Current Biology, 14(24), R1038–R1039.
- Gorgol, J., Stolarski, M. & Jankowski, K. S. (2022). The moderating role of personality traits in the associations between seasonal fluctuations in chronotype and depressive symptoms. Chronobiology International, 39, 1078–1086.
- Levandovski, R. et al. (2011). Depression scores associate with chronotype and social jetlag in a rural population. Chronobiology International, 28(9), 771–778.
- Crespo Castizo, R. & Antúnez, J. M. (2026). Circadian typology and self-esteem, perceived social support and life satisfaction in a Spanish population sample. Behavioral Sleep Medicine, 24(3), 358–370.
- Antúnez, J. M. (2020). Circadian typology is related to emotion regulation, metacognitive beliefs and assertiveness in healthy adults. PLoS ONE, 15(3), e0230169.
- Antúnez, J. M., Navarro, J. F. & Adan, A. (2015). Circadian typology is related to resilience and optimism in healthy adults. Chronobiology International, 32(4), 524–530.