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Seasonal affective disorder (SAD)

Published by Bupa's health information team, June 2008.

This factsheet is for people who have seasonal affective (or mood) disorder (SAD), or who would like information about it.

SAD is a type of depression with a seasonal pattern, occurring most commonly in the winter months.

About SAD

Many people have changes in their sleep patterns, energy levels and mood in the autumn and winter. Indeed, many people can feel "low" during long periods of grey days the winter. However, this unhappiness can develop into SAD. Mild forms of SAD are commonly referred to as "winter blues" but you can have a more severe form and become unable to function in winter without treatment.

About one in 100 people in the UK get SAD, most commonly between the ages of 18 and 30, although it can develop at any age. More women are affected than men.

Symptoms of SAD

If you have SAD your symptoms often get worse in the autumn and winter when the days are shorter, and clear up in spring and summer. You are more likely to get SAD the further away you live from the equator as daylight hours become fewer. You may get SAD in the summer months but this is much less common.

The symptoms of SAD can vary from person to person, and are similar to those that develop in other types of depression. For more information, see Related topics. The most common symptoms include:

  • a low mood for most of the day
  • lethargy
  • needing more sleep and sleeping more than usual
  • eating more than usual, especially craving carbohydrates, leading to weight gain
  • irritability
  • anxiety
  • loss of interest in sex (libido)
  • mood swings and excessive energy in spring/summer - but this is less common

If you have these symptoms during the winter months, you should see your GP.

Causes of SAD

The exact cause of SAD isn't fully understood at present, although there are theories.

SAD may be related to changes in the amount of daylight during the autumn and winter. One theory is that light stimulates a part of the brain called the hypothalamus, which controls mood, appetite and sleep. In people with SAD, lack of light and a problem with certain brain chemicals and hormones prevents the hypothalamus from working properly.

  • A chemical called serotonin has a role in "lifting" the mood. It's thought that people with SAD may have abnormally low levels of chemicals such as serotonin in winter.
  • A hormone called melatonin slows down the body clock, and affects sleeping and mood patterns. People with SAD may respond to a decrease in light by secreting more melatonin than people without SAD. However, medicines designed to suppress the secretion of melatonin don't stop the symptoms of SAD, so this isn't the only factor.

If you have a close relative with SAD, you may be more likely to develop it.

Diagnosis of SAD

Your GP is a good first point of contact. He or she will ask about your day-to-day life and symptoms. One bout of the "winter blues" doesn't automatically mean you have SAD. But, if you have regular symptoms over three or more consecutive years in autumn/winter which clear in the spring, the diagnosis may be SAD.

Your GP may also want to rule out other forms of depression.

Treatment of SAD

Self-help

There are a number of steps you can take to reduce the effects of SAD. Wherever possible, you should:

  • try to find time each day to get outside
  • sit near windows when you are inside
  • take regular, moderate exercise - for more information on exercise, see Related topics
  • eat a well-balanced diet - for more information on eating a healthy diet, see Related topics
  • decorate your home in light colours
  • leave any major projects until summer and plan ahead for winter
  • not put yourself under stress and learn relaxation techniques

Medicines

Your GP may recommend antidepressant medication normally used for other forms of depression. For more information, see Related topics.

If your GP prescribes antidepressants, you may only need to take them during the autumn/winter season, instead of all year round.

Other treatments

Light therapy (also called phototherapy)

Research has shown that exposure to bright, artificial light can improve symptoms in about eight in 10 people with SAD. The aim is to provide bright summer light to stimulate a change in the levels of chemicals and hormones which affect the mood (see Causes).

Bright light is delivered by devices including:

  • a specially made light box - these range in size
  • light caps or visors that are worn on the head like a baseball hat
  • dawn simulators - these are in the form of a bedside light, connected to an alarm clock that mimics a sunrise and wakes the user gradually

The light is at least 10 times stronger than that from normal light bulbs. It's very similar to natural daylight and it won't harm your eyes, unlike strong ultraviolet (UV) light. You should never use homemade light units, such as tanning lights or beds for light therapy. The light given off by these units is high in UV rays and can harm your skin and eyes.

The recommended exposure time to bright light depends on the power of the light source. An effective dose is 5,000 lux per day, given as 2,500 lux for two hours or 10,000 lux for 30 minutes each day, during the autumn and winter months (where lux is a measure of the intensity of light).

Light box treatment can be done in your own home or office. Light boxes aren't available on the NHS but you can buy or hire one - contact the SAD Association (see Further information) for a list of suppliers.

Most people notice an improvement in symptoms within three to four days. You should continue to have light therapy every day until spring - when there are more daylight hours.

Light therapy has few side-effects but they can include headache, irritability, and in rare cases, it can make you feel sick.

You should get advice from your GP before starting light therapy.

Talking therapies

Talking therapies are also available, which include cognitive behavioural therapy (CBT). CBT is a short-term psychological treatment that helps to change the way you think, feel and behave. CBT is a combination of two types of therapy:

  • cognitive therapy, which helps with thinking processes such as unwanted thoughts, attitudes, and beliefs (called cognitive processes)
  • behavioural therapy, which focuses on behaviour in response to those thoughts

For more information, see Related topics.

Help and support

Tell your family and friends about the condition and its effects so that they are able to help and support you. You may find it helpful to join a support group. Knowing that you are not alone and that help is available can be a great comfort.

Related topics

Further information

Sources

  • Seasonal Affective Disorder (SAD). Mental Health Foundation. www.mentalhealth.org.uk , accessed 8 January 2008
  • Understanding seasonal affective disorder. Mind. www.mind.org.uk, accessed 8 January 2008
  • Simon C, Everitt H, Birtwistle J, Stevenson B. Oxford Handbook of General Practice. Oxford, 2002
  • Seasonal Affective Disorder. SAD Association. www.sada.org.uk, accessed 8 January 2008
  • Lurie SJ, Gawinski B, Pierce D. Seasonal affective disorder. Am Fam Physician 2006; 74:1521-1524. www.aafp.org/afp

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr W H Simpson, MBBS, General Practitioner, and by Bupa doctors. It has also been reviewed by Mind. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: June 2008

 

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