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Everything you need to know about seasonal affective disorder (SAD)

Seasonal affective disorder (SAD) refers to depression that occurs during certain seasons.

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05 February 2026

Seasonal affective disorder (SAD) refers to depression that occurs during certain seasons. It is sometimes called winter depression because it often happens in the winter and can be more severe during the winter months.

While it’s common to feel a bit more tired and to sleep slightly more in winter, persistently feeling depressed during any particular season is not something that should be ignored. 

Around 3 in every 100 people in the UK experience seasonal affective disorder. However, there’s support and treatment available, so you don’t need to manage your symptoms alone. 

Here, we will explore the symptoms, risk factors, diagnosis and treatment of SAD.

What is seasonal affective disorder? 

Seasonal affective disorder refers to persistent feelings of low mood and depression that occur during certain seasons. 

In the UK, most cases of SAD happen during the autumn and winter months when the days are shorter and there is less sunshine. However, in rare cases, SAD can occur in the spring and summer. 

Symptoms of seasonal affective disorder

Common symptoms of SAD include: 

  • Having a persistently low mood and trouble concentrating
  • Feeling irritable, tired and sleepy in the daytime
  • Feeling worthless and guilty
  • Losing interest in activities that you normally enjoy, including sex
  • Putting on weight and craving carbohydrates (eg bread, potatoes, rice, pasta, etc)
  • Sleeping more and struggling to wake up in the morning

Symptoms are often worse in the winter months and improve as the days get longer and brighter when spring begins.

These symptoms can have a significant impact on your quality of life and shouldn’t be shrugged off as the “winter blues”. 

What causes SAD?

The exact cause of SAD is not known, but it’s clear that reduced exposure to sunlight is involved and affects the brain. 
It’s thought that part of the brain called the hypothalamus may stop working as well.

This could affect the production of 2 hormones: increasing levels of melatonin, which makes you feel sleepy, and decreasing levels of serotonin, which boosts your mood.

The effect on the hypothalamus may also disrupt your body’s internal 24-hour clock, which is known as your circadian rhythm. This clock controls your sleep–wake cycle, and when it’s disrupted by reduced exposure to sunlight could make you sleep more.

Your genes also likely affect whether or not you develop SAD as the condition can run in families. 

Risk factors for SAD

Stressful situations can make you feel low. For example, Christmas can be a difficult time if you have lost a loved one or have financial difficulties. 

Having negative feelings that are caused by a specific situation does not mean you have SAD. Nevertheless, high periods of stress can make existing symptoms of SAD more severe. 

Other risk factors for SAD include: 

  • Having a family history of SAD
  • Having another type of depression
  • Living far away from the equator — this means you will be exposed to less sunlight in autumn and winter

Low vitamin D levels — vitamin D increases the production of serotonin in the brain, which helps boost mood 

Getting a diagnosis of SAD

If you are concerned that you have SAD, you should see your GP.

They will ask you about your symptoms and when they occur, and whether you have a family history of SAD or other mental health conditions. They will also ask you about your sleep patterns, diet, mood and lifestyle. 

In addition, they will ask whether you have noticed any changes in your behaviour, thoughts or activity levels during different seasons, and if these changes interfere with your normal activities and your enjoyment of things. 

It can take time to reach a diagnosis of SAD as a clear pattern of when the symptoms come and go needs to be established. 

A diagnosis can usually be reached when it becomes clear that your depression occurs around the same time each year for at least 2 years, and the depression goes away during the rest of the year. 

Treating seasonal affective disorder

There are 4 main treatments for SAD: 

  1. Changes to your lifestyle — this includes exercising regularly, finding ways to better manage your stress levels and spending more time in natural sunlight
  2. Daily phototherapy, also known as light therapy — sitting in front of a light box for 30–60 minutes every morning to mimic exposure to natural sunlight 
  3. Talking therapies — this includes a range of different therapies such as counselling and cognitive behavioural therapy (CBT) 
  4. Taking antidepressants eg selective serotonin reuptake inhibitors (SSRIs)

Common misconceptions about SAD

Although the term SAD is widely known, there is less awareness of the severity of the condition. It is not merely the “winter blues” and can have a detrimental effect on someone’s quality of life. 

This can make it more challenging for individuals with SAD to get their friends and family to understand that they are dealing with a type of depression. 

How to manage symptoms of SAD

Living with SAD

If you know you are likely to feel very tired during certain months of the year, try to prepare meals beforehand and freeze them. This way, on particularly challenging days, you won’t need to worry about cooking. 

It’s also important to talk about how you’re feeling. This can be difficult, especially at first. If you don’t feel able to talk to loved ones, you can call the Samaritans, Sane or CALM. You can also write about how you’re feeling in a diary. 

Journaling can be a useful tool for identifying patterns of behaviour, both in terms of what makes you feel better and what makes you feel worse. This can help you better prepare mentally and practically for when your symptoms become more intense eg by scheduling more rest time or re-arranging activities that you know will increase your stress levels. 

Supporting a loved one with SAD

One of the most important ways you can support someone with SAD is simply to let them know that you are there for them and to keep reminding them of this by staying in touch. 

Let them know that you are there to listen to them when they feel able to talk to you about their feelings. You do not need to provide any solutions — sometimes this can trigger feelings of guilt. 

When speaking to someone with SAD, avoid comparing their struggles with SAD to common feelings people have when the weather is rainy, overcast or cold. This can give the impression that you do not think their condition is serious. 

It’s also helpful to avoid using overtly positive or negative terms when describing the weather eg lovely weather, miserable weather, etc. 

If your loved one hasn’t yet sought professional help, encourage them to speak to their GP. You can also ask them what they think makes them feel better and try to support them in engaging in these activities. Try to be flexible when making plans to spend time with them as their symptoms can be unpredictable.

Supporting someone with SAD can at times feel overwhelming. So don’t forget to also look after your own mental health and seek support when you need it.