Seasonal Affective Disorder and Sleep: What you Should Know

The English Romantic poet, Percy Bysshe Shelley, once said: "If winter comes, can spring be far behind?" And for some, the three months of dark and cold can be very difficult, with only the thought of sunnier days to help them through it. Limited daylight, cold conditions and a bare landscape can affect us emotionally, making us feel more tired, unmotivated, and even depressed. In this blog, we’ll offer practical evidence-based advice on how to deal with a mood shift in winter. Although it cannot replace any medical advice, it should help you cope with your mood during the coldest season of the year.

What is Seasonal Affective Disorder – and How is it Different from ‘Winter Blues’?

Winter Blues

The ‘winter blues’ is a colloquial term, referring to a milder seasonal slump – feeling a bit down or sluggish as days get shorter. It doesn’t significantly impair daily life and usually improves with simple lifestyle changes such as exercise, exposure to more daylight and scheduling enjoyable activities.

Subsyndromal SAD

S-SAD is a milder, seasonal mood problem with the same pattern as Seasonal Affective Disorder. Symptoms reliably worsen in winter and lift in spring – but they don’t meet full criteria for a major depressive episode. It lies somewhere between the so-called ‘winter blues’ and full SAD.

SAD

Coined by Norman Rosenthal in the 1980s, Seasonal Affective Disorder (SAD) is a type of depression that follows a predictable seasonal pattern, starting in late autumn or winter and lifting in spring. Symptoms can last about 4 to 5 months and include low mood, lack of energy, changes in sleep, increased appetite, and loss of interest in socialising and hobbies. 1 in 3 people say they struggle with SAD, and 1 in 10 have a confirmed diagnosis of SAD.

How to do a SPAQ Screening

The Seasonal Pattern Assessment Questionnaire (SPAQ) is a short self-report screener that asks how much your sleep, social activity, mood, weight, appetite, and energy change across seasons. It’s widely used to flag possible Seasonal Affective Disorder (SAD) and subsyndromal SAD, but it’s not a diagnosis on its own.

1. Ask the six seasonality indicators. Rate how much the season changes your sleep, social activity, mood, weight, appetite, and energy on a 0-4 scale (0 = no change, 4 = extremely marked).
2. Record problem severity. Rate how much these seasonal changes are a problem overall (0 = none, 1 = mild, 2 = moderate, 3 = marked, 4 = severe).
3. Note timing. Write down which months you feel are the worst and which ones you feel the best.
4. Check pattern consistency. Has this same seasonal pattern occurred for at least two consecutive years? (Yes/No).
5. Find out your Global Seasonality Score (GSS). Sum the six 0–4 items: GSS range = 0–24.

0–7 → Low seasonality

8–10 → Possible subsyndromal SAD

11+ with problem rating more than 2 with a consistent pattern of more than 2 years → Screen-positive for SAD and refer to a clinicianSomeone rates: sleep=2, social=1, mood=3, weight=2, appetite=2, energy=3 → GSS = 13; problem rating = 3; worst in Dec–Feb, best in May–Aug, same pattern for more than 2 years → screen-positive.

Who’s most at risk of SAD?

Even though anyone can be at risk of SAD, statistics show there are some groups who are more likely to be affected by seasonal change:

Women

The World Health Organisation has found that women are more likely to suffer from SAD compared with men, with depression being about 1.5 times more common among women than among men.

Young adults

The WHO also revealed that suicide is the third leading cause of death in 15–29-year-olds.

Those living far from the equator

According to the NHS, a lack of sunlight prevents the hypothalamus, part of the pituitary gland in our brain, from working properly, and those living at higher altitudes receive less direct sunlight.

People who already have depression, anxiety or bipolar disorder

Those who have an existing mental health disorder will be more susceptible to SAD as they struggle with feelings of low mood throughout the year. The Cleveland Clinic cites that lower serotonin levels make them more likely to suffer from SAD.

Workers who have limited exposure to daylight

Serotonin levels get a boost from vitamin D. Since sunlight helps produce vitamin D, less sun in the winter can lead to a deficiency. Insufficient vitamin D can affect serotonin levels and mood, especially among workers who spend limited time outdoors.

How SAD Disrupts Sleep

SAD disrupts your sleep by messing up your internal body clock, or circadian rhythm. We’ve explored this in terms of the science behind SAD.

Light, the circadian clock, and melatonin

The shorter, darker days mean you feel sleepy late at night, and you struggle to wake up in the morning. In the winter, you receive a melatonin signal at the wrong time; the hormone tells your body it’s dark due to limited daylight, which means you start to wind down earlier than in the summer. This leads to fatigue during the day and grogginess in the morning.

Serotonin, mood, and sleep architecture

Serotonin is a key regulator of mood, energy, appetite, and sleep–wake timing. In SAD, there’s evidence that the serotonin system is seasonally off. Science Direct have cited that serotonin dysfunction is a core feature for those with SAD, and there’s less serotonin available for signalling to the brain. REM sleep duration and amount can be altered, with reduced serotonin levels leading you to enter REM earlier and stay in it longer. This means you get poorer-quality sleep, which affects your mood.

Common sleep symptoms in SAD

If you’ve experienced the following symptoms for more than two to three weeks, you could have SAD-related sleep issues.

Insomnia – Difficulty falling asleep due to anxiety and racing thoughts

Hypersomnia – Sleeping more than usual, not feeling sufficiently rested after a night’s sleep and napping during the day

Non-restorative sleep – Wake up feeling groggy, little motivation for the day, not refreshed after a long night’s sleep

Early wakings – Waking up early and not being able to go back to sleep

Daytime fatigue – Feeling sleepy or drowsy, especially when it’s dark or overcast and relying on caffeine and sugar to keep awake during the day

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What are some strategies to improve sleep in winter?

Here are some tried and tested ways to improve your sleep during the darker months of the year.

Embrace the great outdoors

Go for a walk within 30–60 minutes of waking for at least 10-20 minutes. Dr Ritz, our Sleep Expert, spoke to the BBC Radio 2 programme on the subject of SAD. She mentioned exposure to daylight in the morning as being very important, “I’d always recommend that as soon as you wake to try and get ten minutes of daylight, and even if you can’t get yourself outside, stand next to your window for ten minutes to really try to set your circadian rhythm and let that daylight in.”

Reinvigorate your mornings

Wake up at the same time every day. Dr Ritz also advises waking up at the same time, “keep a fixed wake-up time, the brain loves predictability, even on the weekends, keep that wake-up time to a one-hour window.”

Bright-light therapy

Invest in a lightbox that emits 10,000 lux to help reset your body clock and improve your mood. 

Self-care rituals

Prioritise an evening routine that supports melatonin: dim lights 2–3 hours before bed and limit bright screens. Scented candles help create a low-light ambient setting.

Exercise

Release endorphins! Exercise promotes sleep; make sure any rigorous activity is completed 2–3 hours before bed.

Room setup and good sleep hygiene

Dr Ritz says, “Have that wind-down window. We sleep when we feel safe, so clear any mental clutter by journaling, or use cognitive reframing skills, resting without sleeping is still restorative.” Create a cool, dark, quiet bedroom environment, keep a consistent bedtime, avoid caffeine too close to lights out and introduce a wind-down ritual.

Sleep diary

A journal or diary can help you understand your patterns and how they could be linked to your mood.

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What if these strategies do not help with my mood?

If SAD is having a significant impact on your health and wellbeing, and you’re unable to carry out your everyday activities, speak to your GP. They will discuss ways to help you manage the symptoms of SAD. They may advise Cognitive Behavioural Therapy (CBT) to target negative thoughts or even a course of antidepressants.

Conclusion

Seasonal Affective Disorder and sleep are closely linked. When the seasons change, and there’s less daylight, your body clock, mood, and sleep patterns can all be thrown off at once. Poor sleep can worsen SAD symptoms, and SAD symptoms can in turn make it harder to fall or stay asleep, creating a frustrating cycle of fatigue, low mood, and reduced motivation.

The brighter news is that there are many ways to break that cycle. Find joy in the everyday: light exposure, a regular sleep schedule, daytime activity, and a calming wind-down routine all support healthier sleep during the darkest days. For some people, professional treatments such as light therapy, talking therapies, or medication are also important parts of feeling better. Winter brings with it darker days and less sunlight, yet it can be a time to recharge and reset in preparation for brighter days.

Fact-checked by: Dr Ritz Birah