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Seasonal affective disorder (SAD)

Seasonal affective disorder (SAD) is a seasonal form of depression. This means your symptoms occur at the same time every year, usually from September to April.

If your sleep patterns, appetite and mood change every year in the winter months, you may have SAD. SAD is also called the ‘winter blues’. It affects around two in every 100 adults in the UK. The symptoms usually appear for the first time in people in their 20s, but children can also be affected. Women are 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 Symptoms of SAD

    If you have SAD, your symptoms will usually begin in early September each year. They may be triggered by low levels of daylight as autumn sets in. Your low mood may then disappear in the spring, usually around April, as the amount of daylight increases.

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

    SAD symptoms are similar to those triggered by other types of depression. Your symptoms are likely to include: 

    • low mood losing interest in your usual activities 
    • finding it difficult to concentrate 
    • low energy levels (lethargy) 
    • finding it difficult to wake up in the morning 
    • needing more sleep and sleeping more than usual 
    • eating more than usual, especially craving carbohydrates, which can make you gain weight 
    • losing interest in sex (loss of libido) 
    • depression and anxiety 
    • mood swings in the summer

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

    If you think you have SAD, speak to your GP.

  • Diagnosis Diagnosis of SAD

    Your GP will ask you about your day-to-day life and your symptoms. 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 have recurring bouts of depression at the same time each year that get better in between these times, then you may have SAD. SAD is usually treated in the same way as other forms of depression. Treatment includes:

    Some people find that light therapy helps their SAD symptoms but doctors still don’t know how well it works.

  • Self-management of SAD Self-management of SAD

    If your SAD symptoms are mild, you may find that some simple lifestyle measures can help. You should take these steps as soon as you notice you’re craving carbohydrates or have low energy levels around September.

    You may be able to help your symptoms by:

    • putting aside some time each day to go outdoors 
    • doing some regular low-impact exercise 
    • working in bright conditions, such as near a window 
    • increasing the light levels in your home 
    • going for a walk every day in daylight 
    • eating a healthy balanced diet 
    • learning relaxation techniques and not putting yourself under stress 
    • taking 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.

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  • Light therapy for SAD Light therapy for SAD

    Some people may benefit from light therapy. It’s important to be aware that there isn’t much evidence to support the use of light therapy as a conventional treatment. So, if you’re interested in trying it, it’s likely that you’ll 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 would like to get a lightbox, you may be able to borrow, buy or hire one. You should use a lightbox that’s been designed for therapy for SAD. 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. You can also use a light visor that you wear on your head.

    Most doctors recommend using light therapy at an intensity of 10,000 lux for 30 to 60 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 usually need to spend in front of it. You should try to use your lightbox within an hour of waking up in the morning.

    If light therapy works for you, you may notice your symptoms improve within five days and disappear after one or two weeks. Sometimes though, it can take up to six weeks to work. Light therapy doesn’t have many side-effects but you may find that it causes 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).

    You can also try using 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, you may want to use it every autumn, to stop your symptoms appearing in the first place.

  • Medicines for SAD Medicines for SAD

    Your GP may recommend that you try antidepressant medicines that are often prescribed for other forms of depression. They may suggest that you take these medicines while you’re using light therapy.

    Antidepressants work best for SAD if you start taking them before your symptoms begin, and keep taking them until the spring.

  • Cognitive behavioural therapy for SAD Cognitive behavioural therapy for SAD

    Cognitive behavioural therapy (CBT) is one of the most successful talking therapies for depression. It may help 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 changes the way 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. The number of sessions you have will depend on whether your SAD is mild or severe. After each session, you may be given some homework, such as keeping a diary.

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

  • Causes Causes of SAD

    You may more likely to develop SAD if one of your parents, siblings (brothers or sisters) or children has the condition. But doctors still don’t know why some people are more prone than others to SAD symptoms.

    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.

    People with SAD may also have a problem with their production of certain brain chemicals and hormones. 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 during the night and early morning. Melatonin causes an irresistible urge to sleep.

  • Do I need to look directly at the light when I use a lightbox? Do I need to look directly at the light when I use a lightbox?


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

    More information

    You should sit close to the lightbox – less than a metre away. To make sure you get the benefit, you must be awake with your eyes open. You shouldn’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.

  • What is the best type of light therapy? What is the best type of light therapy?


    There are several light therapy devices available. You may need to try a few to find out which one’s right for you.

    More information

    Light therapy devices are available from different manufacturers and they all work slightly differently. So you may wish to try out the device at home (if possible) 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.

    A lightbox is most helpful if you use it at breakfast time. You can use it while you read a book, watch television or eat breakfast. If you only have time to use light therapy in the evenings, a lightbox may not be the best choice for you. Using a lightbox after 5.00 pm may mean you find it hard to get to sleep afterwards.

    If you struggle to wake up on dark winter mornings, you may find a dawn-simulating alarm clock is helpful. You can use this as a bedside lamp that simulates the sunrise. You set it to come on dimly around an hour before you wake up. The light gradually gets brighter, waking you up slowly.

    You can also buy a light visor that you wear on your head. This may be useful if you travel a lot or want to move about and do things during light therapy.

    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.
  • Other helpful websites Other helpful websites

    Further 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.


    • Seasonal affective disorder. PatientPlus., reviewed 12 September 2013
    • Mental health. Oxford Handbook of General Practice (online). Oxford Medicine Online., published April 2014
    • Seasonal affective disorder. BMJ Best Practice., reviewed 30 March 2015
    • Kurlansik S, Ibay A. Seasonal Affective Disorder. Am Fam Physician 2012; 86:1037–41
    • Depression treatment and management: Bright-light therapy. Medscape., reviewed 21 July 2015
    • Seasonal affective disorder. Royal College of Psychiatrists., accessed 4 November 2015
    • Depressive illness. Oxford Handbook of Psychiatry (online)., published March 2013
    • Choosing a lightbox – our 10 point check list. SAD Association., accessed 4 November 2015
    • Cognitive Behavioural Therapy. Royal College of Psychiatrists., accessed 4 November 2015
    • Cognitive and Behavioural Therapies. PatientPlus., reviewed 2 April 2014
    • Gupta A, Sharma PK, Garg VK, et al. Role of serotonin in seasonal affective disorder. Eur Rev Med Pharmacol Sci 2013; 17(1): 49–55.
    • Pineal gland and circadian rhythms. PatientPlus., reviewed 6 September 2013
    • Depression in adults: recognition and management. National Institute for Health and Care Excellence (NICE), October 2009.
    • Depression. NICE Clinical Knowledge Summaries., published October 2015
    • Nussbaumer B, Kaminski-Hartenthaler A, Forneris CA, et al. Light therapy for preventing seasonal affective disorder. Cochrane Database of Systematic Reviews 2015, Issue 11. doi:10.1002/14651858.CD011269.pub2.
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