When the Clocks Fall Back: Daylight Saving Time and Mood

This weekend the clocks fall back an hour. It’s usually treated as the easy clock change, the one that hands you an extra hour of sleep. The research tells a more mixed story: neither change is as simple as it sounds, and the fall change in particular seems to matter for mood.

What the Research Shows

Most of the research looks at the spring change, when clocks move forward and an hour of sleep disappears. Findings from the days after that change include:

• Less sleep. On the Monday after the spring change, US workers slept about 40 minutes less than on other days, and the sleep loss can build up across the following week.
• More fatal car crashes. A large US study found fatal crash risk rose about 6% in the days after the spring change, fading over the following week. Results vary by country, and a study from Great Britain didn’t find the same rise.
• A small rise in heart attacks. A review of seven studies found a modest increase after the spring change, but not in the week after the fall change.
• More workplace injuries. A study of US mining injuries found more, and more serious, injuries on the Monday after the spring change, and no difference after the fall change.

The fall change looks gentler on those measures, but it isn’t free. There’s little evidence that people actually get the extra hour of sleep, and waking earlier relative to the body’s clock for several days can add up to a small net loss across the week. Mood is where the fall change stands out. A large study from Denmark found that hospital diagnoses of depression rose by about 11% after the fall change, with the increase fading over roughly 10 weeks. The spring change showed no similar rise. The researchers suggested that the sudden earlier sunset, marking the start of a long stretch of short days, may explain it.

These are findings across large groups of people, not a prediction of what will happen to you. Most people get through the change with nothing worse than a few groggy days. But for some people, especially those whose mood is sensitive to sleep and light, it’s worth planning around.

Why an Hour Can Matter

The issue isn’t really the hour itself but what it does to your body clock. Light and dark have the biggest influence on your circadian rhythms, the roughly 24-hour cycles that shape sleep, hormones, appetite and body temperature. A clock change moves your work and family schedule overnight, but it doesn’t move the light or your internal timing. For a few days the two are out of step, a bit like a very mild case of jet lag.

Some people feel this more than others. If you’re already short on sleep, you have less in reserve. And if you have bipolar disorder or a history of depression, changes in sleep and daily rhythm can affect mood, so the clock change deserves more attention.

Why It Matters for Mood

In bipolar disorder, sleep matters a great deal. Research shows that poor sleep can trigger and predict manic episodes. If you live with bipolar disorder, it’s worth treating the clock change as a time to protect your sleep on purpose and keep an eye on your mood for the first several days afterward.

For depression, the fall change also marks the start of the darker months. Earlier sunsets and shorter days are part of why some people’s mood drops through late fall and winter, and for some that’s seasonal affective disorder, a depressive episode that comes back around the same time each year. Our posts Winter and Your Mood and Seasonal Affective Disorder (SAD): More Than Winter Blues go into what helps, and our depression guide covers treatment.

For adults in Burlington County and across New Jersey looking for a psychiatrist, our board-certified psychiatric nurse practitioners look at sleep and daily rhythms alongside mood. A clock change, a new work schedule or a run of short nights can be part of the picture, and it helps to spot those patterns.

What Helps This Weekend

• Go by the new clock from Sunday. Get up and go to bed at your usual times on the new clock, and keep your wake time steady, even after a poor night. Waking around the same time each day helps keep sleep on track.
• Get daylight, ideally in the morning. Morning light plays a central role in keeping your body clock from drifting later. With darker evenings ahead, getting outside earlier in the day matters more.
• Go easy on naps. A long or late nap can make it harder to fall asleep at the new bedtime.
• Keep an eye on alcohol. It may help you fall asleep, but it disrupts the second half of the night.
• Expect a few off days. Feeling a bit groggy or out of sorts for several days is normal, not a sign that you’re coping badly.
• Watch your mood if you have a history of episodes. If something is shifting, contact your provider rather than waiting for your next appointment.

If your sleep stays off for more than a couple of weeks after the change, that’s worth bringing up too. Ongoing sleep problems are something we look at as part of sleep disorder care.

Beyond the Clock Change

The clock change is a twice-a-year example of something that matters all year. A steady body clock supports mood, and it’s one of the things you can actually influence. Regular sleep and wake times, daylight in the morning and regular meal times all help keep it steady.

What throws it off is usually ordinary: irregular schedules, sleeping in on weekends, late nights on bright screens, travel and alcohol. Weekends deserve a special mention. Sleeping much later on Saturday and Sunday than during the week creates a small, repeating mismatch between your body clock and your schedule, sometimes called “social jet lag.” Studies have linked social jet lag with depression, as well as with heart and metabolic problems. If your mood is sensitive to sleep, keeping your weekend wake time close to your weekday one is a simple thing to try.

So if your mood tends to follow your sleep, the clock change is a good reminder to pay attention to something worth looking after all year.

Getting the Household Through It

The clock change affects everyone at home, and it tends to go more smoothly when the whole household plans for it together.

• Children need time to adjust too. Keeping their wake time steady and expecting a few unsettled days helps.
• Meals can move to the new clock along with sleep, since meal timing also affects the body clock.
• Mornings can feel rushed in the first days, so a little extra time helps.
• The first few days can be kept lighter where possible, since the weekend change gives you a day or two to settle before the week gets busy.
• Evening screens are worth winding down at night, since bright light late in the evening can push your body clock later.

None of this is dramatic. It’s just treating a known disruption as something to plan around rather than something that catches you by surprise twice a year.

Frequently Asked Questions

Does the clock change really affect health?

Research links the spring change with less sleep, more fatal car crashes in US data, a small rise in heart attacks and more workplace injuries in the days afterward. The fall change looks gentler on those measures, but one large study found a rise in depression diagnoses after it. These are findings across large groups of people, not a prediction for any one person.

Don’t I get an extra hour of sleep in the fall?

In theory. In practice, research finds little evidence that people actually sleep an extra hour, and waking earlier relative to your body clock for several days can mean a small net loss across the week. The earlier darkness can also affect mood as the days get shorter.

How long does it take to adjust?

Usually several days to about a week, sometimes longer, especially if you’re already short on sleep. Keeping your wake time steady and getting daylight earlier in the day can help.

Should I be concerned if I have a mood disorder?

It’s worth taking seriously, especially with bipolar disorder, where poor sleep can trigger manic episodes. Protect your sleep around the change, watch your mood for the first several days and talk with your provider if something is shifting. For depression, the start of the darker months is also a good time to check in about any seasonal pattern.

If clock changes, sleep or shorter days reliably affect your mood, a psychiatric evaluation can help sort out what’s going on, and medication management can help you stay on track through the darker months. Our depression guide covers the bigger picture.

This article is for general educational purposes only. It does not constitute medical advice, does not establish a provider-patient relationship, and is not a substitute for individual evaluation, diagnosis, or treatment by a qualified clinician. If you’re in crisis or thinking about harming yourself, call or text 988 (Suicide & Crisis Lifeline), any time, day or night. In an emergency, call 911 or go to the nearest emergency room.