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Seasonal Affective Disorder (SAD)

IntroductionSeasonal affective disorder 2

For thousands of years, people have noticed that the seasons can affect our mood. It was not until the 1980s, however, that the term Seasonal Affective Disorder (SAD) appeared. It is used for people who, although they sometimes become depressed in the  summer, regularly become depressed in autumn and winter. 


SAD has a lot in common with other types of depression. It would probably be helpful to read our general leaflet on Depression before reading this leaflet about SAD.


What is seasonal affective disorder (SAD)?

SAD is a type of depression with a particular pattern - it starts in the autumn or winter and stops in the spring and summer, regularly each year.  For this reason it is sometimes called “recurrent winter depression”.


Many of the symptoms of SAD are the same as those of  'ordinary' (non-seasonal) depression (as described in more detail in the Depression leaflet).  These symptoms include:

  • low mood (often worse in the mornings)
  • lack of energy
  • less “get up and go”
  • less interest in life
  • being unable to enjoy things
  • irritability
  • seeing other people less
  • less interest in sex.

But the symptoms of SAD are slightly different. In non-seasonal depression, people commonly sleep less and eat less. In SAD, they usually sleep more and eat more


If you have  SAD, you may find it very difficult to wake up on a winter's morning and can often feel sleepy during the day. You may crave chocolate and high carbohydrate foods, such as white bread or sugary foods. If you have SAD, you probably won't be doing as much physically, so it's easy to put on weight during the winter.


SAD-type depression recovers in the spring.Indeed, around a third of people with SAD become mildly high in mood (hypomanic, as described in the leaflet in Bipolar Disorder) during the spring and summer.


Who is affected by SAD?

Like other types of depression, SAD is most common in women during the years when they can have children.  It is about three times more common in women than it is in men.  SAD does occur in children and in older adults, but this is fairly rare.


It is not common in people who live near the equator – the further away from the equator you live, the greater the risk of having SAD.


How common is it?

Many of us will be mildly affected by the winter with symptoms of feeling slightly tired, sleeping a bit more and perhaps gaining some weight.  It is a bit like hibernation in animals. If your symptoms are bad enough to interfere with your life, you may well have SAD.  In the UK, about 3 people in every 100 have significant winter depressions.


What causes SAD?

It seems to be a simple lack of daylight in winter. We now live much more of our lives indoors and so see less sunlight. It is thought that a lack of such light affects how serotonin works in the brain and that this can make us more likely to become depressed.


Other effects of SAD

Some symptoms of SAD can create extra problems which make you feel even worse – 'vicious circles':

  • If you feel tired all the time, you will probably do less – and lack of exercise can make depression worse.
  • If you are eating more, you may put on too much weight.
  • Sleepiness, lack of motivation and irritability can all cause problems at home, socially, and at work. You don't get round to doing things that need to be done, and this can add stress to your life.

Some of the self-help measures mentioned below can help to prevent these 'vicious circles' from becoming too big a problem.


Managing SAD


These self-help measures will usually be enough to help mild degrees of SAD, but should also be used even with more severe SAD.

  • Go outside as much as possible during the darker months so you can see more daylight.
  • Carry on any regular exercise you do - best outside since this gives you daylight as well.
  • Tell your family and friends so that they can understand what is happening and be more supportive.
  • Remind yourself that after Christmas the days will be getting longer and spring is on the way.

Light therapy

This is done with a lightbox, to try to make up for the shortage of daylight in winter. The light given out is like sunlight, but without the ultraviolet rays so it is not harmful to the skin or the eyes.

From the time that symptoms start in autumn, you should use a lightbox for 30 minutes to an hour each day. It is most helpful if you use it at breakfast time.  Light therapy works quite quickly. If it is going to help, most people will notice some improvement in the first week.


Fortunately, any side-effects are usually mild. You may notice you have a headache, nausea or blurred vision.  These can be reduced by just moving further away from the lightbox – but not too far. The further your eyes are away from the light, the less bright it becomes, so you may need to use it for longer to get the same effect.  It is usually best not to use a lightbox after 5.00 pm because you may then find it hard to get to sleep.


Dawn-simulating alarm clocks are also used.  These come on dimly about an hour before waking up time and gradually get brighter. They can be particularly helpful if you find it hard to wake up on winter mornings.


Other light devices include:

  • desk lights for people with desk jobs
  • light visors: these are shaped like a baseball cap with small lights shining into the eyes.


Antidepressants are generally helpful in SAD. Any medication which would make people more tired or sleepy should be avoided, and so SSRI antidepressants are usually used (more details in leaflet on antidepressants).  The best evidence is for the use of sertraline, citalopram or fluoxetine.  In SAD, it is usual to start antidepressants in the autumn and stop them in the spring.


Cognitive behavioural therapy (CBT)

There is some evidence that CBT may be helpful to treat winter depression and to prevent it coming back in future winters. For more details, see our leaflet describing CBT.


What is the best treatment?

For mild symptoms, the self-help measures described in this leaflet will usually be enough to help.

For more severe symptoms, the first choice will usually be between a lightbox and antidepressants.  The choice will often depend on what is available, what is convenient and what each person prefers.


Only a few studies have compared light therapy and antidepressants, but it seems that both treatments work equally well. When one treatment is not enough, light therapy and antidepressants can be used together.


Further information

  • Seasonal Affective Disorders Association (SADA) at PO Box 989, Steyning, BN44 3HG
  • Winter Blues, Revised Edition:  Everything you need to know to beat Seasonal Affective Disorder by Norman E. Rosenthal, Guilford Press, New York, 2006 is an excellent source of further information.

Suppliers of lightboxes and related devices include:

  • Lumie, 3 The Links, Trafalgar Way, Bar Hill, Cambridge, CB23 8UD
  • Lightbox UK, 49 Dalsetter Avenue, Glasgow, G15 8TE

These companies will supply lightboxes for 3 to 4 weeks on a trial (sale or return) basis.



Anonymous (2009) Management of seasonal affective disorder. Drugs and Therapeutic Bulletin, 47, 128-132.

Golden, BN et al (2005) The efficacy of light therapy in the treatment of mood disorders:  a review and meta-analysis of the evidence.  American Journal of Psychiatry, 162, 656-662.

Eagles, JM (2009) Light therapy and seasonal affective disorder. Psychiatry, 8, 125-129.

Produced by the Royal College of Psychiatrists' Public Education Editorial Board.

Series editor: Dr Philip Timms

Main author: Professor John Eagles

Service user/carer input: Depression Alliance

Illustration: Lo Cole:

This leaflet reflects the best available evidence available at the time of writing.

© May 2010. Review date: May 2012.
Royal College of Psychiatrists. This leaflet may be downloaded, printed out, photocopied and distributed free of charge as long as the Royal College of Psychiatrists is properly credited and no profit is gained from its use. Permission to reproduce it in any other way must be obtained from The College does not allow reposting of its leaflets on other sites, but allows them to be linked to directly.

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