How to sleep well in the dark winter months

Key takeaways

• The problem is too little light at the right time. Your body clock sets itself by daylight, and in winter most people get very little of it, especially in the morning.

• Even a gray day is far brighter than indoors. Overcast daylight is many times brighter than a typical office or living room, so a morning walk does more than any ordinary lamp.

• Most people sleep only a little more in winter. Studies find the seasonal difference is small, often a matter of minutes a night. Feeling heavy and sluggish for weeks is worth taking seriously.

• Keep your wake-up time steady. Sleeping in on dark weekend mornings pushes your body clock later and makes Monday harder.

• Light therapy helps winter depression. A light box used in the morning is a standard treatment for seasonal affective disorder, but check with a doctor first if you have bipolar disorder or an eye condition.

Why dark winters affect sleep

Your body runs on an internal clock of roughly 24 hours, and light is the main signal that keeps it in step with the day. Bright light in the morning nudges the clock earlier, so you get sleepy at a reasonable hour that night. Light in the evening pushes it later.

Winter takes away much of the morning signal. The sun rises late, many people leave for work or school in the dark, and the hours of daylight are spent indoors. On top of that, the clocks falling back in late October or early November moves sunset an hour earlier.

The gap between outdoor and indoor light is bigger than it feels. According to figures compiled by light researchers, daylight on an overcast day measures around 10,000 to 20,000 lux. A typical office is lit to 300 to 500 lux, and a living room to 50 to 200. The eye adjusts so well that indoor light seems bright, but to your body clock it’s dim.

Do we sleep more in winter?

A little, for most people. In a survey of 1,388 adults in Japan, sleep was longest in winter, but only about 11 minutes longer than in summer. A 2023 study of 188 patients at a Berlin sleep clinic found about 30 minutes more dreaming (REM) sleep in winter than in spring. Their total sleep also looked longer in winter, though that difference wasn’t large enough to be sure of.

How much light you get makes a difference. When researchers had volunteers live in long winter nights of 14 hours of darkness in a lab, they slept about 10.6 hours a night, compared with 7.6 hours on summer-length nights, and their nightly melatonin lasted longer. In a small 2017 study of people camping in winter, light during waking hours averaged more than 10,000 lux while camping, compared with about 750 lux at home, and their body clocks shifted much earlier while camping.

Large studies of people’s sleep timing also show seasonal shifts. An analysis of 55,000 people found that on days off, sleep timing tracked the time of dawn through the year, except when daylight saving time was in force.

When winter tiredness is more than tiredness

For some people, the winter slump is something more. Seasonal affective disorder is a form of depression that comes back at the same time each year, usually starting in fall and lifting in spring. According to the National Institute of Mental Health, winter symptoms often include oversleeping, craving carbohydrates, weight gain, and pulling away from other people, alongside low mood.

Studies estimate that between about 1.5% and 9% of adults have it, with more cases farther from the equator, according to a Cochrane review. In a 2001 study, people with seasonal depression made melatonin for longer each night in winter than in summer, while healthy volunteers showed no seasonal change.

If you think you might have seasonal affective disorder, the NHS advises seeing a doctor.

1. Get outside in the morning

Getting daylight in the morning is the most useful thing you can do for your body clock in winter. In a study of about 400,000 adults in the UK Biobank, each extra hour spent outdoors during the day went with finding it easier to get up in the morning and feeling less tired.

Aim to get outside within an hour or two of waking, even when it’s cloudy. A walk to work or school, a coffee by an open door, or a few minutes on a balcony all count. Sitting by a window helps less, since you see only part of the sky.

2. Keep the same wake-up time, even on weekends

Sleeping in feels like the answer to dark mornings, but it makes the problem worse. Sleeping late means missing morning light and getting it later in the day instead, which shifts your clock later. In a 2010 study of teenagers, a typical weekend of late nights and late mornings pushed their melatonin timing about 45 minutes later over a single weekend.

Keep your weekend wake-up time within about an hour of your weekday one. If you’re short on sleep, an earlier bedtime does less damage to your clock than a later morning.

3. Consider a light box or a dawn simulator

If you can’t get outside in the morning, artificial light is the next best thing.

• Light boxes. The NIMH describes the usual treatment for seasonal affective disorder as sitting near a 10,000 lux light box for 30 to 45 minutes each morning. A 2020 review of 19 trials found light therapy reduced symptoms of seasonal depression, and a 2016 review found bright light also helped sleep problems more generally, with a small to moderate effect.

• Dawn simulators. These are bedside lamps that brighten gradually before your alarm goes off. A 2005 review of five trials found they helped seasonal depression, and in a 2001 trial of 95 people, a dawn simulator worked at least as well as a light box.

Light boxes are safe for most people. Bright light therapy can trigger hypomania, according to guidance from light therapy researchers, so people with bipolar disorder should use it only under a doctor’s care. The NIMH also advises talking to a doctor first if you have an eye condition or take a medicine that makes you sensitive to light.

4. Dim the lights in the evening

Evening light has the opposite effect of morning light. It holds back melatonin and pushes your clock later, and it doesn’t take much. In a 2000 lab study, ordinary room lighting of around 100 lux was enough to have half the maximum effect on melatonin.

In the last hour or two before bed, switch from overhead lights to lamps, and keep the room dim. Screens add some light too, but our post on blue light from your phone explains why the time you spend on them counts for more than their color.

5. Exercise earlier in the day

Exercise helps sleep, and a 2015 review found regular exercise improved sleep quality by a moderate amount. Timing also affects your clock, a little. A 2019 study found that exercise at 7am or in the early afternoon shifted the body clock earlier, while exercise between 7pm and 10pm shifted it later. If you can exercise outdoors in the morning, you get the light and the activity together.

6. Keep the bedroom cool and not too dry

It’s tempting to turn the heat up in winter, but a cool bedroom is better for sleep. Our guide to the best temperature to sleep at covers the ideal range.

Heated winter air is also dry, and very low humidity can irritate the eyes and airways. If you wake with a dry throat or stuffy nose, a humidifier may help. Keep it clean, following the maker’s instructions.

7. Go easy on holiday drinking and late meals

Winter is party season, and alcohol is a common sleep disrupter. A 2020 analysis of long-term studies found that people who drank were more likely to develop sleep problems later. Our post on alcohol and REM sleep explains how drinking changes the night.

Large meals close to bedtime may not help either. In a small 2011 study, people who ate more of their food late in the evening tended to take longer to fall asleep and slept less efficiently, though the study couldn’t show cause and effect.

What about vitamin D?

Many people take vitamin D in winter, and it’s sensible advice for bone health in places with little winter sun. Its effect on sleep is less clear. A 2022 review found that vitamin D supplements improved sleep quality scores, but only three trials could be pooled, and the evidence was limited. The NIMH notes that studies of vitamin D for seasonal depression have had mixed results.

Frequently asked questions

Why am I so tired in winter?

Mostly because of less daylight. With dark mornings and days spent indoors, your body clock gets a weaker signal and drifts later, so mornings feel harder. If the tiredness comes with low mood that lasts for weeks, talk to a doctor about seasonal affective disorder.

Is it normal to sleep more in winter?

A little more is normal. Studies find most people sleep only slightly longer in winter, often by only a few minutes. Sleeping much more than usual and still feeling exhausted can be a sign of seasonal depression.

Do light therapy lamps work?

For seasonal affective disorder, yes. Light therapy is a standard treatment, usually with a 10,000 lux light box for 30 to 45 minutes each morning. Check with a doctor first if you have bipolar disorder or an eye condition, or take medicines that make you sensitive to light.

What time should I go outside in winter for light?

In the morning, ideally within an hour or two of waking. Morning light shifts your body clock earlier, which makes it easier to fall asleep at night and get up the next day.

Does vitamin D help you sleep?

The evidence is limited. A few small trials found it improved sleep quality scores, but there isn’t enough research to recommend it for sleep alone.

How do I stop oversleeping in winter?

Keep the same wake-up time every day, get outside or near a bright light soon after waking, and avoid sleeping in late on weekends. A dawn simulator can make dark mornings easier.