Seasonal affective disorder (SAD)

Seasonal affective disorder

Mental health

Seasonal affective disorder (SAD) is a form of depression which affects people in winter, but not in summer. For people in the northern hemisphere, symptoms start around September, are worse during December, January and February when the days are shortest, and start to improve in March. People living in the southern hemisphere are affected during their winter months. The condition is extremely rare in those living within 30 degrees latitude of the equator and is most common in those living in higher latitudes (greater than 50 degrees north or south).

For some, symptoms are sufficiently severe to disrupt their lives and cause considerable distress. For others, symptoms are mild, causing them to sleep slightly more and dislike the dark mornings. Those with mild symptoms are said to have sub-syndromal SAD.

It is estimated that SAD affects about half a million people in the UK each winter. Women are more likely to be affected than men, and it tends to occur most frequently in those between the ages of 18 and 30. About 1 in every 8 people suffers from sub-syndromal SAD.

SAD appears to be caused by an upset in the balance of chemicals in an area of the brain called the hypothalamus, due to the lack of bright sunlight in winter. This would explain why those who live within 30 degrees latitude of the equator, where daylight hours are bright and constant, do not suffer from SAD, while those who live in more northerly or southerly latitudes where winter nights are long, have the highest proportions of the population affected.

Two chemicals in the brain are thought to be responsible for SAD, melatonin and serotonin. The production of melatonin, a substance that makes us drowsy, is suppressed by bright light entering the eyes, causing us to waken. The lack of bright light on dull days inhibits this natural waking process. Exposure to bright light also appears to increase the production of a substance called serotonin, a chemical that carries signals between the nerves in the brain. Lack of serotonin is known to be a cause of depression. A decrease in the level of serotonin due to insufficient bright light may be a cause of SAD.

For people in the northern hemisphere, symptoms start around September, are worse during December, January and February when the days are shortest, and start to improve in March. The speed of improvement depends on the intensity of light in the Spring; the brighter the days, the faster the recovery.

Symptoms of SAD include:

• Sleep problems - oversleeping but not refreshed, cannot get out of bed, needing a nap in the afternoon
• Overeating - carbohydrate craving leading to overweight
• Depression - despair, misery, guilt, anxiety, normal tasks become frustratingly difficult
• Family problems - avoiding company, irritability, loss of libido, loss of feeling
• Lethargy - too tired to cope, everything an effort
• Physical symptoms - often joint pain or stomach problems, lowered resistance to infection
• Behavioural problems - especially in young people

In sub-syndromal SAD, symptoms such as tiredness, sleeping and eating problems occur, but depression and anxiety are either absent or mild.

Medicines

Logically, as the cause of SAD is a lack of bright light, the best and simplest treatment is light therapy. Exposure to very bright light, created by means of a light-box that produces light at least ten times the intensity of ordinary domestic lighting, for up to 4 hours each day brings relief of symptoms within 3 or 4 days. Relief is sustained provided use of the light-box is continued throughout winter. All that is required is to sit about 2 to 3 feet from the light-box, allowing the light to shine into the eyes. Normal activities such as reading or working can carry on as normal. Dark glasses should not be worn as this prevents the light from entering the eyes, which in turn prevents the brain chemical balance from being restored.

For people with milder symptoms a 'dawn simulator' alarm clock, with a light which comes on slowly in the morning to copy a natural sunrise and to give the body-clock a signal to start the wakeup process may be sufficient.

Taking a winter holiday to a sunny climate, whether up the mountains on a skiing holiday, or to somewhere hot can also help relieve symptoms. Taking regular walks outdoors during the winter months is also recommended to ease symptoms.

If symptoms are particularly troublesome, antidepressants may be used. SSRIs or selective serotonin reuptake inhibitors such as citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine and sertraline are the preferred type of antidepressant as these drugs increase the level of serotonin that is thought to be depleted in SAD. Other antidepressants have proved less effective as they have a tendency to increase lethargy and so add to, rather than ease the symptoms of SAD.

The herbal remedy St John's wort has also been used as this too appears to increase levels of serotonin.

If you think that you or a relative is affected by SAD, ask your pharmacist for advice. Light-boxes, suitable for light therapy of SAD and sub-syndromal SAD are not available on an NHS prescription but you may be able to obtain one through your local pharmacy.

St John's wort can also be obtained from your pharmacy without a prescription, but it is important that you tell your pharmacist if you are taking any other medicines as St John's wort may interact with them and increase their side effects.

Your pharmacist will also be able to recommend some simple changes in lifestyle that will help.

If your symptoms are interfering with your life, your pharmacist will advise you to see your doctor who is able to prescribe stronger antidepressants.

It is always sensible to talk to your doctor if you believe you are suffering from a depressive illness. Keeping a record of when symptoms first appear and then ease, will help your doctor make a diagnosis if it is SAD.

Logically, as the cause of SAD is a lack of bright light, the best and simplest treatment is light therapy. Exposure to very bright light, created by means of a light-box that produces light at least ten times the intensity of ordinary domestic lighting, for up to 4 hours each day brings relief of symptoms within 3 or 4 days in about 85% of people affected by SAD. Relief is sustained provided use of the light-box is continued throughout winter. All that is required is to sit about 2 to 3 feet from the light-box, allowing the light to shine into the eyes. Normal activities such as reading or working can carry on as normal. Dark glasses should not be worn as this prevents the light from entering the eyes, which in turn prevents the brain chemical balance from being restored.

Light-boxes, suitable for light therapy of SAD and sub-syndromal SAD are not available on an NHS prescription but you may be able to obtain one through your local pharmacy.

For people with milder symptoms a ‘dawn simulator’ alarm clock, with a light which comes on slowly in the morning to copy a natural sunrise and to give the body-clock a signal to start the wakeup process may be sufficient.

Taking a winter holiday to a sunny climate, whether up the mountains on a skiing holiday, or to somewhere hot can also help relieve symptoms. Taking regular walks outdoors during the winter months is also recommended to ease symptoms.

• Take regular outdoor exercise in winter
• Take a winter holiday if possible

SADA, the Seasonal Affective Disorder Association, is a voluntary organisation and registered charity founded in 1987 to support and advise people with SAD, and to inform the public and health professionals about the condition. The SADA information pack contains full details of SAD treatments, where to obtain light therapy equipment and how to use it.

SADA
PO Box 989
Steyning
BN44 3HG
www.sada.org.uk


Reviewed on 6 June 2011

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