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.
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.
Self-help for SAD
- Get outside in daylight every day, ideally in the morning. Even a cloudy day is much brighter than indoors.
- Sit near windows at home and work.
- Exercise regularly, outdoors 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.
- 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.
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 or treatment isn’t helping. If you’re having thoughts of suicide or self-harm, call NHS 111 and choose the mental health option, contact Samaritans on 116 123, or call 999 in an emergency.
If it’s mainly tiredness, see why am I so tired in winter?
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.
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.
This guide is general information, not medical advice.
