Source: French to English Tester Published on: 2026-03-31
Source: The Conversation – France in French (3)– By Oliver Serrano León, Director and professor of the Master’s in General Health Psychology, European University
Last weekend, we switched to daylight saving time. Scientific data, however, show that moving the clock forward can affect sleep, concentration, mood, and psychological well-being for several days. But, in most cases and in the absence of mental health-related disorders, these discomforts are temporary and are not alarming signs.
This Sunday, March 29, a familiar scene repeated itself: the official calendar marked the start of legal summer time. In Spain, specifically, the time is moved forward by one hour simultaneously across the entire territory, although the official time differs between the peninsula and the Canary Islands,as provided by the royal decree governing the time change.
(Daylight saving time was established in France following the 1973-1974 oil crisis. The dates for switching to summer time and then to winter time are nowharmonized in all member countries of the European Union, ed.).
On paper, this seems to be a minor adjustment. But for the brain, this is not always the case.
This is not just a bad evening to get through
From the point of view of psychology, what matters is not so much the “lost” hour as the discrepancy that occurs between social time and biological time. Our body functions according tocircadian rhythms, that is to say internal oscillations that regulate thesleep, awakening, body temperature, appetite, and a large part of emotional regulation. When the official time is suddenly advanced, the body does not always accompany this change at the same pace. This is why many people feel for a few days a sensation similar to a small [“jet lagsocial »]: they have trouble falling asleep, getting up, and performing as if nothing had happened.
One of the most common mistakes is to think that the change simply amounts to sleeping one hour less on Sunday morning. Available data indicate that the reality is more complex.A recent analysis of 27 studiesconcludes that the transition to daylight saving time is associated with negative effects on the duration and quality of sleep, as well as increased daytime sleepiness.
This effect also seems more pronounced in people with an evening chronotype, that is to say those who tend to go to bed and get up later. It is not just about having a bad night: in some cases, the adaptation can take several days.
This slight lack of sleep has noticeable psychological consequences. Most often, it does not manifest as a major clinical problem, but rather as an accumulation of daily “microdegradations”: more moments of inattention, less concentration, slower mental processes, reduced tolerance to frustration, and irritability.
Thescientific literature on sleep, circadian rhythms, and mental healthshows that disturbances in rest and circadian synchronization affect not only our sleep, but also our attention, cognitive functions, and mood. In other words: when the biological clock is disrupted, some of our psychological resources are also affected.
Attention, errors, and fatigue: the most immediate effects
In spring, the change of season was also associated with an increase in fatigue and a decrease in performance in tasks that require sustained vigilance. It is no coincidence that in some studies, effects have been observed in contexts where a slight decrease in vigilance has significant consequences.
Onestudy published inCurrent Biologyhas revealed that the transition to daylight saving time was associated with a 6% increase in the risk of fatal road accidents in the United States. This figure does not mean that all people will drive noticeably worse. But it reinforces a fundamental idea: even a seemingly modest disruption of sleep can have real effects on attention and reaction time.
Not everyone is affected in the same way
And the observation is the same as for almost all psychological phenomena: not the entire population is affected in the same way. People who are used to going to bed late, those who already suffer from sleep deficit, or who have rigid early morning schedules generally feel this shift more strongly.
Adolescents also constitute a particularly sensitive group. A study on sleep at this age after the switch to daylight saving time showed thatthis adaptation can harm restand be associated with a decrease in cognitive capacities. These results are not surprising. Adolescence is already accompanied by a biological tendency to delay bedtime. However, the time change goes exactly in the opposite direction.
Can the time change affect mood?
Can the time change also affect mood? Yes, but caution is advised. It would be exaggerated to claim that moving the clock forward by one hour “causes” psychological disorders by itself. The data are more nuanced. A well-known study conducted in Denmark, for example, observed a11% increase in unipolar depressive episodesAthe autumn after the time change, but not the one that takes place in the spring, (that is to say after the switch to daylight saving time, editor’s note). More recently, a demographic study conducted in England found nothat little evidence of an acute effect of the transition to daylight saving timeon events related tomental healthregistered in the health services.
A reasonable interpretation leads to not being alarmist: for most people, the time change will not cause a clinical problem, but it can temporarily affect mood, energy levels, and emotional regulation, especially if a preexisting vulnerability was already present.
This caution is consistent with what is known about the link between biological rhythms and mental health. Recent studies indicate that, in people suffering from mood disorders,circadian phase disruptions can precede symptoms related to mood disorders. This does not mean that the time change is the sole cause, but it helps to understand why a seemingly insignificant adjustment can be more noticeable in some people than in others.
How to mitigate the impact
The best way to approach the time change is to not make a big deal out of it, without ignoring it either. Research on circadian adaptation reminds us that morning light is one of the most powerful signals to advance the biological clock and that evening light tends to delay it.
This is why it is useful to expose oneself to natural light in the morning, to avoid any intense light stimulation in the evening, and to pay particular attention to getting good rest on the days before and after the time change. It can also be helpful to gradually advance the bedtime by 15 to 20 minutes in the days leading up to it, rather than waiting for the body to readjust on its own from one day to the next.
Ultimately, the time change serves as a reminder, admittedly inconvenient but useful: the mind does not function independently of sleep, light, or biological rhythms. One hour may seem insignificant, but when those sixty minutes result in poorer quality sleep, increased fatigue, reduced concentration, and heightened irritability, it goes beyond just adjusting the clock and also becomes a matter of psychological well-being.
Oliver Serrano León does not work for, advise, hold shares in, or receive funds from any organization that could benefit from this article, and has declared no other affiliation than his research organization.
–ref. Sleeping one hour less: the effects of the time change on alertness, mood, and psychological well-being –https://theconversation.com/sleeping-one-hour-less-the-effects-of-time-change-on-alertness-mood-and-psychological-well-being-279606