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Seasonal Affective Disorder (SAD)


Expert reviewer, Dr Rahul Bhattacharya, Consultant Psychiatrist
Next review due May 2021

Seasonal affective disorder (SAD) is a seasonal form of depression. This means you get symptoms at the same time every year, usually around autumn and winter. That’s why it’s sometimes known as ‘winter blues’, or ‘winter depression’.

If your sleep patterns, appetite and mood change every year, usually in the winter months, you may have SAD. It affects around three in 100 people in the UK. 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.

If you have a low mood every autumn and winter, speak to your GP. There are several treatments you can try to help ease your SAD symptoms.

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Symptoms of seasonal affective disorder (SAD)

If you have SAD, your symptoms will usually begin in the autumn each year – possibly triggered by low levels of daylight. You might then start to feel much better in the spring, as the days get longer and lighter.

Some people have SAD symptoms in the spring and summer months instead. The symptoms then disappear in the winter. But this is much less common.

The symptoms of SAD are similar to those for other types of depression. You may have symptoms each season that include:

  • feeling low and losing interest in your usual activities
  • feeling hopeless, helplessness, 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 have some physical symptoms too, such as headaches, palpitations (being aware of your own heartbeat) and aches and pains.

Although less common, in spring and summer you might have what are called manic periods where you feel happy, energetic and much more sociable. This can also happen if you have a condition called bipolar disorder.

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

Diagnosis of seasonal affective disorder (SAD)

Your GP will ask you about your day-to-day life and your symptoms and may refer you to a specialist for further support. 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. SAD is usually treated in the same way as other forms of depression.

Treatment for seasonal affective disorder (SAD)

Treatment for SAD can be similar to that for depression, as well as some additional options. These may include:


You can learn more in our blog: Tips to treat seasonal affective disorder (SAD).

If you get SAD in summer, it’s best to discuss a personalised treatment plan with your doctor.

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 – you could go for a walk every lunchtime, for example.
  • Do some regular exercise, preferably outside, as this is known to help with depression.
  • Work in bright conditions, such as near a window.
  • Eat a regular healthy balanced diet.
  • Make an effort to regularly get together with friends and family.
  • Take a holiday in a sunny place.

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. You may find it helpful to join a support group too. Knowing that you’re not alone and that help is available can be a great comfort.

Light therapy for seasonal affective disorder (SAD)

Some people find that light therapy improves their SAD symptoms but more evidence is needed to support use of light therapy as a conventional treatment. If you’re interested in trying it, you’ll probably need to buy a lightbox yourself.

Light therapy exposes you to bright artificial light to make up for the shortage of natural daylight in winter. The idea is that providing bright light encourages your body to make certain chemicals and hormones that can boost your mood.

The light comes from a specially made lightbox. If you’d like to try light therapy, it’s important to use a lightbox that’s been specifically designed for SAD therapy. This is because the light in these lightboxes is much brighter than a normal light bulb. It's similar to natural daylight, but it won't harm your eyes or skin because it doesn’t include ultraviolet (UV) light.

Doctors recommend using light therapy at an intensity of 10,000 lux for 30 minutes every day. A lux is a measure of the intensity of the light you receive at a certain distance away from the light source. The brighter the light, the less time you need to spend in front of it. It’s best to use your lightbox within an hour of waking up in the morning if possible. And try not to use your lightbox after 5.00pm because you may find it hard to get to sleep afterwards.

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. Light therapy doesn’t have many side-effects but you might get headaches or blurred vision. It may also make you feel tired and irritable. Light therapy isn’t recommended if you have some eye diseases or take medicines that make your skin sensitive to sunlight (such as certain antibiotics). Read the patient information that comes with your lightbox and ask your GP or optician if you’re unsure.

You could also try a dawn-simulating alarm clock. This is a timed bedside light that mimics a sunrise to wake you up gradually. This can help if you find it hard to wake up in the morning during the winter.

If light therapy helps you, use it every autumn as it may stop your symptoms appearing in the first place.

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 therapies for seasonal affective disorder (SAD)

Cognitive behavioural therapy (CBT) is a talking therapy that can change how you think, 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 can change how you think and what you do. It 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 are more prone to SAD symptoms than others. But you may be more likely to develop SAD if one of your parents or siblings (brothers or sisters) has the condition.

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're more likely to have SAD if you live further away from the equator. This is because the farther from the equator you are, the fewer daylight hours there are in winter.

If you have SAD, your body may not produce certain brain chemicals and hormones correctly. A chemical called serotonin plays an important role in mood, appetite and sleep. It's thought that people with SAD may have abnormally low levels of serotonin in the winter. People with SAD may also produce too much of a hormone called melatonin later in the night and for longer than normal during the early morning. Melatonin causes an irresistible urge to sleep.

Frequently asked questions

  • No. The light needs to reach your eyes but you don't need to stare at the lightbox directly.

    You should sit close to the lightbox – check the instructions for how close you need to be. To make sure you get the benefit, you must be awake with your eyes open. Don’t wear tinted lenses or anything else that stops light from reaching your eyes.

    You can do other activities while you're using light therapy, such as eating or reading. But keep your body facing towards the light.

  • There are several light therapy devices available, including lightboxes, dawn-simulating alarm clocks, and light visors that you wear on your head. You may need to try a few to find out which one works for you.

    Light therapy devices are available from different manufacturers and they all work slightly differently. See if you can try out the device at home before you commit to buying one. Whichever form of light therapy you use, it’s important to choose a device that comes from a reputable seller and meets medical guidelines.

    Different devices give off different intensities of light. Those with a lower power or intensity aren't necessarily any less effective – you just need to use them for longer to get the same effect.

  • Some research has suggested that having low levels of vitamin D may affect your chances of getting SAD.

    You can get vitamin D from your diet, but your body also makes it naturally when your skin is exposed to sunlight. The amount of vitamin D your body makes depends on how strong the sunlight is. So you’ll make more in the summer months, than during the winter. Vitamin D is also thought to affect chemicals in your brain such as serotonin, and low levels have been linked to symptoms of depression.

    In the UK, taking vitamin D supplements to treat SAD isn’t currently recommended because the evidence isn’t strong enough. More research is needed for doctors to recommend them.


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Related information

    • Mental Health Foundation
      The Mental Health Foundation is a charity that carries out research and offers information about many areas of mental health. This page complements our content about SAD with additional detail about its symptoms and the ways the condition can affect you.
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    • Cognitive behavioural therapy (CBT). Mind. www.mind.org.uk, published October 2017
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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, May 2018
    Expert reviewer, Dr Rahul Bhattacharya, Consultant Psychiatrist
    Next review due May 2021



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