Last updated: October 2026
Seasonal affective disorder (SAD) is depression that comes back at the same time each year, usually in autumn and winter, and lifts in spring. Signs include low mood, losing interest in things, tiredness, sleeping more and craving carbohydrates. The NHS treats it with talking therapies and antidepressants, and some people use a SAD lamp.
Below: SAD symptoms, SAD vs the winter blues, what causes it, SAD lamps and how to use one, other treatments, self-help, and when to get help.
SAD symptoms
The NHS lists these symptoms of seasonal affective disorder:
- Low mood and losing interest in things you usually enjoy
- Feeling guilty, hopeless or worthless
- Feeling restless or irritable, and finding it hard to concentrate
- Eating more, often craving carbohydrates
- Feeling more tired and sleeping more
- Thoughts of suicide or self-harm
Less often, SAD happens in summer instead. A GP will usually consider SAD if your depression comes back at the same time of year for 2 years or more.
When does seasonal depression start?
For most people with SAD, symptoms start in autumn or early winter, as the days get shorter, and improve in spring. Each year tends to follow a similar pattern, so many people notice it coming back around the same month.
- Autumn: the first signs are often small: finding it harder to get up, sleeping more, wanting more carbohydrates and doing less.
- Winter: symptoms are usually at their worst in the darkest months.
- Spring: mood and energy usually lift as daylight returns. Some people feel more energetic than usual in spring and summer.
A less common summer pattern also exists, where symptoms start in late spring or summer and ease in winter. Because the timing is predictable, it helps to plan ahead with your GP before the autumn if you have had SAD before.
Is seasonal depression real?
Yes. Seasonal affective disorder is a recognised type of depression, not just a dislike of winter. The NHS describes it as depression that usually happens in winter, and NICE guidance for depression in adults includes advice for people with winter depression that follows a seasonal pattern.
The Royal College of Psychiatrists estimates that about 3 people in every 100 in the UK have significant winter depression. Many more feel a milder dip in mood and energy, which is usually called the winter blues. The difference is how much it affects your life: SAD gets in the way of work, relationships and day-to-day living, and it is diagnosed by a GP, usually when depression comes back at the same time of year for 2 years or more.
SAD vs the winter blues
| Winter blues | SAD | |
|---|---|---|
| What it is | A common dip in mood and energy in the darker months | A type of depression with a seasonal pattern |
| Effect on life | Mild; you still get on with things | Affects work, relationships and daily life |
| What helps | Daylight, exercise, routine, seeing people | The same, plus treatment from your GP |
If yours sounds more like the first column, see the winter blues.
What causes SAD?
The exact cause isn’t known. The NHS says it’s thought to be linked to less sunlight in winter, which may affect two brain chemicals: melatonin, which makes you sleepy, and serotonin, which affects mood, appetite and sleep. Less light may also disturb your body clock. When the clocks go back, evenings suddenly get darker. See clocks going back and sleep.
SAD lamps: do they work and how to use one
Light therapy uses a bright light box, often called a SAD lamp, to imitate daylight. Many people say it helps, but the NHS says there isn’t enough evidence to know whether it works, so it isn’t usually available on the NHS. If you want to try one:
| Check | What to look for |
|---|---|
| Brightness | 10,000 lux |
| Safety | UV-free, with a UKCA or CE mark |
| How to use | As the maker directs. Most people use it in the morning |
| Check first | Speak to a GP if you have an eye condition or take medicines that make you sensitive to light |
Wake-up lights that slowly brighten before your alarm are different. They’re gentler and can make dark mornings easier, but they aren’t as bright as a light box.
SAD treatment on the NHS
- Talking therapies such as cognitive behavioural therapy (CBT). In England, adults can refer themselves to NHS Talking Therapies.
- Antidepressants, prescribed by a GP.
- Light therapy, which some people buy themselves.
Many people need treatment each winter to stop symptoms coming back, so it’s worth planning ahead with your GP before the darker months.
How to fight seasonal depression
These are the practical steps from NHS and Royal College of Psychiatrists self-help advice, roughly in the order most people find easiest to start. They work best alongside treatment from your GP if your symptoms are more than mild.
- Get outside in daylight every day, ideally in the morning. Even a cloudy day is much brighter than indoors. A walk at lunchtime counts too.
- Make your home and workspace brighter. Sit near windows at home and work, and open the curtains as soon as you get up.
- Consider a SAD lamp. If you try light therapy, most people use a 10,000 lux lamp in the morning and avoid using it late in the day. Our SAD lamp guide covers brightness, distance and timing.
- Make dark mornings easier. A dawn simulator brightens slowly before your alarm. It isn’t a light box, but some people find waking up easier. See our sunrise alarm clock guide.
- Exercise regularly, outdoors in daylight if you can.
- Keep the same sleep and wake times, including weekends. See sleep hygiene.
- Stay in touch with friends and family, and keep doing the things you enjoy, even in a smaller way. Tell the people close to you what is happening so they can support you. If you feel cut off, see loneliness: how to feel more connected.
- Plan ahead for stressful events in winter.
- Go easy on alcohol, and put screens away before bed.
- Take vitamin D in winter. The NHS advises everyone to consider 10 micrograms a day from October to March. It isn’t a treatment for SAD, but most of us don’t make enough in winter. See vitamin D in winter.
- Ask about talking therapy. CBT is used for SAD, and in England adults can refer themselves to NHS Talking Therapies without seeing a GP first.
- See your GP about antidepressants if self-help isn’t enough. For SAD they are often started in autumn and stopped in spring.
If what you have sounds milder, our guide to beating the winter blues has more everyday ideas. See also how to relieve stress and why am I always tired?
When to get help
See a GP if you think you have SAD, if it is affecting your daily life, or if treatment isn’t helping.
If you need support now
- Samaritans: call 116 123, free, any time of day or night.
- NHS 111: call 111 and choose the mental health option for urgent help.
- NHS Talking Therapies: adults in England can refer themselves for talking therapy such as CBT.
- 999 or A&E: if your life or someone else’s is at risk, or someone has seriously hurt themselves or taken an overdose.
Related guides
- If it’s mainly tiredness, see why am I so tired in winter?
- Natural ways to boost serotonin.
- Loneliness: how to feel more connected.
- Hygge.
- See our winter wellness guide.
- If you work from home, see our tips for working from home in winter.
- For the signs of depression and 15 ways to lift your mood, see low mood vs depression.
- When is Blue Monday 2027, and is it real.
- Circadian rhythm, daylight and light boxes.
- For other reasons you might be sleeping more than usual, see oversleeping: causes and when to see a GP.
- The best time to take vitamin D in the UK.
- For simple ways to support mood chemistry through a UK winter, see happy hormones: what they are and how to boost them.
- For a full guide to brightness, distance, timing and what to buy, see SAD lamps: do they work and how to use one.
- Dawn simulators have also been studied in SAD; our sunrise alarm clock guide explains the evidence and how they differ from a SAD lamp.
- People sometimes ask whether CBD has a place here; read what the research shows on CBD and depression.
- Winter low mood is not a reliable sign of deficiency; see the signs of low vitamin D and how a GP tests for it.
FAQs
What are the symptoms of seasonal affective disorder?
Low mood, losing interest in things, feeling hopeless, irritability, tiredness, sleeping more and eating more, returning at the same time each year.
When does seasonal depression start?
Usually in autumn or early winter, as the days get shorter. Symptoms tend to be worst in the darkest months and improve in spring. A less common summer pattern also exists.
Is seasonal depression a real thing?
Yes. Seasonal affective disorder is a recognised type of depression with a seasonal pattern. The NHS and NICE both cover it, and the Royal College of Psychiatrists estimates about 3 in 100 people in the UK have significant winter depression.
How can I fight seasonal depression?
Get outside in daylight every day, ideally in the morning, exercise, keep regular sleep times and stay in touch with people. Some people try a 10,000 lux SAD lamp. If it affects your daily life, see a GP about talking therapies such as CBT or antidepressants.
What does seasonal depression mean?
It means depression that comes and goes with the seasons, most often starting in autumn or winter and lifting in spring. Its medical name is seasonal affective disorder, or SAD.
Is SAD the same as the winter blues?
No. The winter blues is a mild seasonal dip. SAD is a type of depression that affects daily life and may need treatment.
Do SAD lamps work?
Many people find them helpful, but the NHS says there isn’t enough evidence to be sure. Choose a 10,000 lux, UV-free lamp with a UKCA or CE mark.
When should I use a SAD lamp?
Follow the maker’s instructions. Most people use it in the morning. Check with a GP first if you have eye problems or take light-sensitising medicines.
Does vitamin D help SAD?
It isn’t a proven treatment for SAD, but the NHS advises everyone to consider 10 micrograms of vitamin D a day from October to March.
How is SAD treated in the UK?
With talking therapies such as CBT, antidepressants, and sometimes light therapy. Adults in England can refer themselves to NHS Talking Therapies.
Sources
- NHS. Seasonal affective disorder (SAD).
- NHS. Vitamin D.
- NHS. NHS Talking Therapies.
- NHS. Where to get urgent help for mental health.
- Royal College of Psychiatrists. Seasonal affective disorder (SAD).
- NICE. Depression in adults: treatment and management (NG222), recommendation 1.4.39.
- nidirect. Seasonal affective disorder (SAD).
This guide is general information, not medical advice.
