What SAD is
Seasonal affective disorder (SAD) is depression that comes and goes in a seasonal pattern. In most people it starts in late autumn or early winter and lifts in spring. It is now often described as major depression with a seasonal pattern.
The main trigger is thought to be less daylight. Shorter days can disrupt the body clock (circadian rhythm), raise levels of the sleep hormone melatonin, and affect serotonin, a brain chemical linked to mood.
SAD is real and treatable. It is not a weakness, and you do not have to wait for spring.
Winter blues or SAD?
Many people feel a little flatter and more tired in winter. The difference is severity and impact:
| Winter blues | SAD |
|---|---|
| Mild dip in mood and energy | Low mood most of the day, nearly every day |
| You still work, socialise and enjoy things | Loss of interest or pleasure in things you usually enjoy |
| Passes quickly or comes and goes | Lasts weeks, and returns each year |
| Daily life largely unaffected | Affects work, relationships or daily tasks |
Common symptoms
Winter-pattern SAD often includes the usual signs of depression, plus some that are typical of the season:
- Persistent low mood, hopelessness or irritability
- Loss of interest in activities and people
- Low energy and feeling sluggish
- Sleeping much more than usual and struggling to get up
- Craving carbohydrates and gaining weight
- Difficulty concentrating
- Withdrawing from friends and family, sometimes described as feeling like hibernating
If you have thoughts of harming yourself or that life is not worth living, seek help now. Contact a doctor, an emergency number, or a crisis line in your country, such as 988 in the US, Samaritans on 116 123 in the UK and Ireland, or Umang on 0311 7786264 in Pakistan.
Who is most at risk
- People living farther from the equator, where winter days are short.
- Women, who are diagnosed more often than men.
- Young adults; SAD often starts between the ages of 18 and 30.
- People with a personal or family history of depression or bipolar disorder.
Treatments with good evidence
Light therapy
The best-known treatment for winter-pattern SAD:
- A light box giving 10,000 lux of white light, with UV filtered out.
- About 20 to 30 minutes each morning, soon after waking, with the box at the distance the maker recommends, usually 40 to 60 cm (16 to 24 inches) from your face. You do not stare at it; you can read or eat breakfast.
- Many people notice improvement within one to two weeks. It works only while you keep using it through the season.
Side effects are usually mild: eye strain, headache or feeling wired. Check with a doctor first if you have bipolar disorder (light can trigger mania), eye disease, or take medication that makes you sensitive to light.
Talking therapy
Cognitive behavioural therapy (CBT), including a version adapted for SAD, has good evidence. Some research suggests it may reduce the chance of symptoms returning in later winters. Our overview of therapy options explains the types.
Antidepressants
A doctor may suggest an antidepressant, usually an SSRI. People with a clear history of SAD sometimes start medication in early autumn, before symptoms usually begin, on a doctor's advice.
Daily habits that help
These are not a substitute for treatment when SAD is significant, but they help with both SAD and the milder winter blues.
- Get outside in daylight, especially in the morning. Even an overcast day is far brighter than indoor lighting. A lunchtime walk combines daylight and exercise. See our guide to the benefits of walking.
- Keep a steady sleep schedule, getting up at the same time every day. Our sleep quality guide has practical tips.
- Sit near windows at home and at work.
- Stay in touch with people, even when you do not feel like it.
- Plan things to look forward to, especially in January and February.
- Limit alcohol, which worsens mood and sleep.
When to see a doctor
See a doctor if low mood lasts more than two weeks, affects your daily life, or comes back every winter. A doctor can rule out other causes, such as thyroid problems or anaemia, and agree a treatment plan. Do not stop prescribed medication without medical advice.
Key takeaways
- SAD is depression with a seasonal pattern, usually autumn to spring.
- It differs from the winter blues in how severe it is and how much it affects daily life.
- Light therapy, CBT and antidepressants all have good evidence.
- Morning daylight, exercise, routine and social contact help too.
This article is general information, not medical advice. If you are struggling, speak to a doctor or mental health professional.