Seasonal Affective Disorder (SAD)

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What is seasonal affective disorder?

Seasonal affective disorder (SAD) is a condition where you develop symptoms of depression at the same time each year.

• Winter depression is the most common type. In the UK and other countries north of the equator the symptoms usually develop sometime between September and November and continue until March or April. Symptoms tend to be worse in December, January and February.
• Summer depression is much less common. It develops in the late spring and symptoms persist through the summer. It tends to have different features and may have a different cause to the common 'winter' type of SAD.

The rest of this leaflet deals only with the winter depression type of SAD.

Who gets seasonal affective disorder?

At least 1 in 50 people in the UK are thought to have SAD. Many more, perhaps as many as 1 in 8 people, have 'winter blues' - a less severe form of the condition. SAD is less common in countries near to the equator where the hours of sunlight are more constant and bright throughout the year.

SAD usually first begins between the ages of 20 to 30, but it can develop at any age. It affects four times as many women as men.

What causes seasonal affective disorder?

The exact cause is not clear. The amount of sunlight affects the number of nerve messages which you send from the eyes to certain parts of the brain. The activity of nerve messages caused by sunlight affect the level of certain brain chemicals (such as serotonin) and hormones (such as melatonin). These chemicals and hormones are thought to affect your 'mood'. So, with less sunlight in the winter months, changes in the balance of certain chemicals and hormones may affect your mood and trigger a depression.

Your genetic makeup may be important too as some people inherit a tendency to develop SAD. About 1 in 7 first degree relatives (mother, father, child, brother, sister) of people with SAD are also affected.

What are the symptoms of seasonal affective disorder?

Symptoms of depression
When symptoms develop in the winter, they are similar to those that occur in others type of depression. The following is a list of common symptoms of depression. You may not have them all, but several usually develop.

• Low mood for most of the day, nearly every day. Things always seem 'black'.
• Loss of enjoyment and interest in life, even for activities that you normally enjoy.
• Abnormal sadness, often with weepiness.
• Feelings of guilt, worthlessness, or uselessness.
• Poor motivation. Even simple tasks seem difficult.
• Poor concentration. It may be difficult to read, work, etc.
• Sleeping problems.
  • Sometimes difficulty in getting off to sleep.
  • Sometimes waking early and unable to get back to sleep.
  • Sleeping too much sometimes occurs (particularly in SAD - see below).
• Lacking in energy, always tired.
• Difficulty with affection, including going off sex.
• Poor appetite and weight loss. Sometimes the reverse happens with increased eating and weight gain. (People with SAD often put on weight - see below.)
• Irritability, agitation, or restlessness.
• Symptoms often seem worse first thing each day.
• Physical symptoms such as headaches, palpitations, chest pains, and general aches and pains.
• Recurrent thoughts of death. This is not usually a fear of death, more a preoccupation with death and dying. Some people get suicidal ideas - "life's not worth living".

Depression is different to the 'ups and downs' from day-to-day that we all have. With depression, symptoms occur each day for at least two weeks. Symptoms also become severe enough to interfere with day-to-day functions. Work and relationships may suffer.

See separate leaflet called 'Depression' for more details about depression.

Some particular features of SAD
If you have SAD you tend to have some of the 'atypical' (less typical) symptoms of depression.

• You tend to put on weight rather than lose weight. This is because many people with SAD develop craving for sweet things and have an increased appetite.
• Rather than difficulty sleeping, you tend to be more sleepy and sleep more.
• Some people with SAD report a feeling of heaviness in the arms and legs.

Without treatment, the symptoms tend to improve and go fairly abruptly in the spring, over a week or so. Some people develop great bursts of energy and creativity in the spring. In a small number of cases, as spring arrives the mood changes from depression into an abnormal 'high' and elated mood (mania or hypomania).

Some people who work in buildings without windows may have SAD symptoms throughout the year. On the other hand, if you have SAD whilst living in the UK, the symptoms may not occur if you move to a country nearer the equator such as southern Spain.

Winter blues
In the winter many people feel more tired, sleep more, put on some weight, and feel a little 'blue'. However, they do not develop the full features of depression to be classed as having SAD. This is called winter blues, and is sometimes called 'sub-syndromal SAD'.

How do you know it is SAD and not the common form of depression?

The diagnosis of SAD is based on you having episodes of depression which have occurred on at least two consecutive years in the winter months. And, symptoms clear in the spring. Also, if you have SAD your symptoms tend to include the 'atypical' features of depression (craving sweet things, increased appetite, weight gain, increased sleepiness).

You, and your doctor, may not realise that you have SAD for several years. This is because recurring depression is quite common. You may have been treated for depression several times over the years before it is realised that you have the seasonal pattern of SAD.

What are the treatment options for SAD?

Light Therapy
Research studies have shown that light therapy can greatly improve symptoms in about 2 in 3 cases of SAD. This is often the first treatment tried. However, this treatment takes time and commitment. See below for details.

Antidepressants
Antidepressant medicines are commonly prescribed for all types of depression, including SAD. They work well to relieve symptoms in about 7 in 10 cases.

Antidepressants do not usually work straight away. It takes 2-4 weeks before their effect builds up fully. A common problem is that some people stop the medicine after a week or so as they feel that it is doing no good. You need to give it time. It is best to persevere if you are prescribed an antidepressant medicine.

There are several types of antidepressants, each with various 'pros and cons'. For example, they differ in their possible side-effects. (The leaflet that comes in the medicine packet provides a full list of possible side-effects.) However, it is thought that 'SSRI' antidepressants are better for treating SAD than other types of antidepressants. SSRI stands for 'selective serotonin reuptake inhibitor'. They work partly by increasing the level of the brain chemical called serotonin which may be low in people with SAD. For more details see separate leaflets called 'Depression' and 'SSRI Antidepressants'.

Other treatments
Talking treatments such as cognitive therapy (if available in your area) is another option which can work well to treat depression. Regular exercise (particularly if done outdoors in the daytime) may also help to ease symptoms.

Some people are treated with a combination of treatments if one treatment alone does not work well. For example, a light box plus an antidepressant.

Light therapy for SAD

What is light Therapy?
This treatment consists of sitting in front of a special bright light for a session each day. Light intensity is measured in lux. Ordinary light bulbs are not strong enough as they only give out 200-500 lux. To treat SAD you need a light source of at least 2500 lux (about 10 times that of ordinary light bulbs).

What does treatment entail
Special light boxes are made for the purpose of treating SAD. Follow the instructions that come with the box. Basically:

• You start treatment in the autumn, as soon as symptoms begin.
• You sit 2-3 feet away from the light box.
• You face the bright light, but you do not have to look directly into it.
• The length of light therapy needed each day varies. If the light source is very powerful (10,000 lux) then 30-45 minutes per day is usually sufficient. With less powerful light boxes, 2-3 hours a day are needed.
• You can do things such as eating, reading, knitting, etc, whilst sitting in front of the light box. Some people with 'desk jobs' are able to get on with their work with a light box in front of them.
• Some studies suggest that treatment in the morning works best, but other studies do not confirm this. So, the best time to do it is the time most convenient to yourself. However, evening sessions cause difficulty with sleeping afterwards in some people.
• Some people have their light therapy session whilst having their breakfast and reading the morning paper, or get up a early to have a session before going to work.

How does light therapy work
The logic is that it 'replaces' the bright sunlight which you normally see in the summer. But, it is not clear exactly how it works. It is not simply extending the length of the daylight hours. In fact, you usually do light therapy sessions at some stage in the daytime, not when it is dark. Bright light affects the retina (back of the eye) which sends nerve signals to parts of the brain. This is thought to affect the level of certain chemicals and hormones which you make in parts of the brain which affect mood.

How quickly does it work?
Most people notice an improvement in symptoms within 3-4 days. Symptoms will stay improved so long as you keep on with treatment every day until spring. In some cases it takes up to 4-6 weeks of treatment for symptoms to improve. It does not work in every case. See your doctor for other treatment options if you do not notice an improvement after 6 weeks.

Is light therapy safe?
It appears to be safe. There is a theoretical risk of damaging the retina (back of the eye). However, there have been no reports of harm with the specially designed light boxes. The light boxes used to treat SAD do not emit much ultraviolet (UV) light which is the main damaging part of sunlight to the skin and eyes. Side-effects occur in some people and include: headaches, difficulty sleeping after an evening session of light therapy, irritability and tiredness.

Note: you should not use sun tan machines as a source of bright light. The light from sun-tan machines gives off a lot of ultraviolet (UV) rays, which can harm your eyes. It is best to use only the light boxes which are made especially to treat SAD.

What about natural sunlight?
Natural sunlight, even on an overcast day in winter, provides more 'lux' than the artificial light source in a light box. So, going for a walk outside every day for 1-2 hours during the daytime may ease symptoms. However, this may not be a realistic option for many people. For example, if you work indoors.

How can I get a light box?
You cannot get a light box on prescription from the NHS. Various companies make them and they cost from about £100. The SAD association (see below) provide a list of suppliers. Some companies will allow you to 'try before you buy' to see if it works for you before you commit to buying a light box.

Does light therapy work for other types of depression?
No. It only works if you have SAD.

Further help and information

SAD Association (Seasonal Affective Disorder Association)
PO Box 989, Steyning, West Sussex, BN44 3HG
Tel: 01903 814942   Web: www.sada.org.uk
A voluntary organisation which informs the public and health professions about SAD and supports and advises sufferers of the illness. It produces a newsletter thrice-yearly, and other publications, has a network of contacts, a lightbox hire scheme, and raises money for research into SAD.

© EMIS and PIP 2004   Updated: May 2003   CHIQ Accredited   

The authors and editors of this article are employed to create accurate and up to date content reflecting reliable research evidence, guidance and best clinical practice. They are free from any commercial conflicts of interest. Find out more about updating.

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