Seasonal Affective Disorder (SAD)

Expert reviewers, Dr Sammad Hashmi, Consultant Psychiatrist and Dr Ade Adeniyi, Bupa Clinics GP
Next review due January 2024

Seasonal affective disorder (SAD) is a type of depression that comes and goes with the changing seasons. This means you get symptoms at the same time every year, usually around autumn and winter. Available treatments include lifestyle changes, light therapy, talking therapies and medication.

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About seasonal affective disorder (SAD)

Many of us are affected by a change in the season, perhaps feeling a lack of energy, changing sleep patterns or low mood in the winter. We may call this the ‘winter blues’. But if these changes interfere with your day-to-day life, you may have seasonal affective disorder (SAD), a form of depression.

The symptoms of SAD and the main types of treatment are like those for other forms of depression. See our sections on symptoms and treatment for more information.

SAD affects up to three in 100 people in the UK at some point in their life. Most people start to get symptoms for the first time in their 20s or 30s, but children can be affected too. Women are about four times more likely to have SAD than men.

Symptoms of seasonal affective disorder (SAD)

If you have SAD, your symptoms will usually begin in the autumn each year and continue through the winter. You then start to feel much better in the spring.

Some people have SAD symptoms in the spring and summer months instead, but this is less common. For more information about summer SAD, see our FAQ section.

The symptoms of SAD are like those for other types of depression. You may have seasonal symptoms that include:

  • feeling low and losing interest in your usual activities
  • feeling hopeless, helpless, worthless, or guilty
  • finding it difficult to concentrate
  • having low energy levels and feeling lethargic during the day
  • feeling indecisive
  • finding it difficult to wake up in the morning
  • sleeping more than usual
  • eating more than usual, especially carbohydrates, which can make you put on weight
  • losing interest in sex (loss of libido)
  • feeling less sociable
  • feeling anxious

You may also have some physical symptoms such as headaches, palpitations (being aware of your own heartbeat), and aches and pains.

If you have any of these symptoms and think you have SAD, contact your GP.

If you have winter SAD, in spring and summer you may have what are called manic periods. This is where you feel happy, energetic and much more sociable. This can also happen if you have a condition called bipolar disorder. If you have these symptoms, your doctor will assess you to see which condition you have.

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Diagnosis of seasonal affective disorder (SAD)

Your GP will ask you about your symptoms – including their timing, how severe they are and how they affect your day-to-day life. They may ask about anything in your life which might mean you’re more likely to have depression. This could include asking if other members of your family have depression.

One bout of the winter blues doesn't automatically mean you have SAD and your GP may want to rule out other forms of depression first. But if you’ve had two or more recurring bouts of depression at the same time of year, that get better in between times, you may have SAD.

Treatment for seasonal affective disorder (SAD)

Treatment for SAD is similar to that for depression, with some additional options. Treatment may include:

  • self-help, including lifestyle changes
  • light therapy
  • medicines (antidepressants)
  • talking therapy (for example, cognitive behavioural therapy)

There’s no strong evidence that one treatment works much better than another. Several treatments may be used together, and which treatment you have may depend on your own preferences. You can find out more about each type of treatment in the sections below.

Self-help for seasonal affective disorder (SAD)

If your SAD symptoms are mild, you may find that making some small changes to your lifestyle can help. Take these steps as soon as you notice any symptoms.

  • Spend more time outdoors in the daylight – for example, you could go for a walk every lunchtime.
  • Do some regular exercise, preferably outside because this is known to help with depression.
  • Work in bright conditions – for example, near a window.
  • Eat a regular healthy balanced diet.

It’s a good idea to tell your family and friends that you have SAD and explain how it affects you. Then they’ll be able to give you help and support when you need it.

See our FAQ section for more information about self-help for summer SAD.

You may find it helpful to join a support group or speak to someone on a mental health helpline too. See our section on other helpful websites for information about organisations which can provide help and advice. Knowing that you’re not alone and that help is available can be a great comfort.

Light therapy for seasonal affective disorder (SAD)

In light therapy, you use a bright artificial light to make up for the shortage of natural daylight in winter. The light comes from a specially made device which gives off much brighter light than a normal light bulb. Doctors recommend using light therapy at an intensity of 10,000 lux for 30 minutes every day. A lux is a measure of how bright the light is.

Getting a light therapy device

If you’re interested in trying light therapy, you’ll probably need to buy a light device yourself. Choose one that is made for treating SAD, comes from a reputable seller and meets medical guidelines.

There are several light therapy devices available, including lightboxes and dawn-simulating alarm clocks. You may need to try a few to find out which one works for you. See if you can try out the device at home before you commit to buying one.

How should I use a lightbox?

Your lightbox should come with instructions on how to use it, including how close to the box you need to be. It’s best to use your lightbox within an hour of waking up in the morning if possible. Try not to use your lightbox after 5.00pm because you may find it hard to get to sleep afterwards.

To get the benefit, you must be awake with your eyes open. You can do other activities while you're using light therapy, such as eating or reading. But keep your body facing the light.

If your symptoms of SAD ease with light therapy, you may be able to spend less time using the lightbox as time goes on. It can be difficult to keep up with your light therapy every day, but you may find your symptoms come back if you stop. You should keep using light therapy until the time of year when your symptoms usually go away on their own.

Does light therapy work?

Some people find that light therapy improves their winter SAD symptoms but doctors aren’t sure yet how well it actually works. If light therapy works for you, you may notice your symptoms improve within a week or two. But sometimes, it can take up to six weeks to work. If light therapy helps you, use it every autumn to stop your symptoms appearing in the first place.

Can light therapy cause any problems?

Although light therapy is like sunlight, it doesn’t have the ultraviolet rays which make sunlight harmful to your skin or eyes.

Any side-effects of light therapy are usually mild. You might get headaches, blurred vision or nausea (feeling sick). It may also make you feel tired and irritable.

Light therapy isn’t recommended if you have some eye conditions or take medicines that make your skin sensitive to sunlight. Read the patient information that comes with your lightbox and ask your GP or optician if you’re unsure.

Medicines for seasonal affective disorder (SAD)

Your GP may recommend that you try antidepressant medicines that are used to treat other forms of depression. A type of antidepressant called selective serotonin reuptake inhibitors (SSRIs) are most commonly used for SAD. Your doctor may suggest that you take these medicines even if you’re already using light therapy.

Antidepressants work best for SAD if you start taking them in the autumn, and keep taking them until the spring.

Talking therapy for seasonal affective disorder (SAD)

Your doctor may recommend a type of talking therapy called cognitive behavioural therapy (CBT). CBT can change how you think and feel, and what you do. It works well for depression, and you may find that it helps you to manage your SAD symptoms. It may even stop your SAD symptoms coming back each year.

CBT aims to identify and challenge how you:

  • think about yourself, the world and other people
  • feel about your thoughts
  • behave in response to your thoughts and feelings

You may have CBT in a group or as a one-to-one session. Each session usually lasts around an hour and you may have one session every week for a number of weeks, depending on your individual circumstances. After each session, you may be given some homework such as doing some exercises.

You can also have CBT sessions using a computer programme or self-help books or even over the telephone.

Causes of seasonal affective disorder (SAD)

Doctors still don’t know exactly why some people get seasonal affective disorder (SAD). It’s probably caused by several different factors acting together, and these may be different for each person.

Your risk of developing SAD may be related to how your body responds to changes in daylight during the autumn and winter. Light stimulates a part of your brain called the hypothalamus. If you have SAD, a lack of light may stop your hypothalamus from working properly. Reduced daylight may delay your body clock, which affects your sleep, body temperature, hormone levels and mood.

You may be slightly more likely to have SAD if you live further away from the equator. The equator is the imaginary line around the earth, halfway between the north and south pole. The farther from the equator you are, the fewer daylight hours there are in winter and the greater the change in daylight hours between seasons.

If you have SAD, your body may not produce certain brain chemicals and hormones correctly.

  • Melatonin. People with SAD may produce too much of a hormone called melatonin during the winter. Melatonin prepares your body for sleep.
  • Serotonin. People with SAD may have abnormally low levels of a chemical called serotonin in the winter. Serotonin plays an important role in mood, appetite and sleep.

Your genes may also play a part. You may be more likely to develop SAD if one of your parents or siblings (brothers or sisters) has the condition.

Frequently asked questions

  • Yes, though it’s more common in autumn and winter. If you have SAD during the summer months, your symptoms start in the spring, continue over the summer but then improve when the autumn arrives.

  • Symptoms of summer SAD can be a little different. People who have SAD in the winter may sleep more than usual, and find that they want to eat more, especially carbohydrates. But if you have summer SAD, you may find it difficult to get to sleep and you may lose your appetite.

    If you have SAD in the summer months, it’s best to discuss a personal treatment plan with your doctor. Self-help would include staying out of the sun rather than seeking daylight. But instead of staying at home all the time, which might make you feel isolated, try to find activities to do in other indoor places.

  • You can get vitamin D from your diet, but your body also makes it naturally when your skin is exposed to sunlight. We know that many people with seasonal affective disorder (SAD) have low levels of vitamin D in their bodies. And some research has suggested that having low levels of vitamin D may affect your chances of getting depression.

    Does this mean that taking supplements of vitamin D relieve symptoms of SAD? There have been studies to look at this but the results are mixed. So, at the moment, doctors aren’t sure if taking vitamin D supplements helps to treat SAD.

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  • Reviewed by Dr Kristina Routh, Freelance Health Editor, January 2021
    Expert reviewers, Dr Sammad Hashmi, Consultant Psychiatrist and Dr Ade Adeniyi, Bupa Clinics GP
    Next review due January 2024