What is seasonal affective disorder?

Seasonal affective disorder (SAD) is a condition where you develop symptoms of depression in the darker winter months each year.

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.

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 affects 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.

Some people seem to inherit a tendency to develop SAD. So, your genetic makeup may be important too. About 1 in 7 first-degree relatives (mother, father, child, brother, sister) of people with SAD is 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 the non-seasonal ordinary type of depression. The following is a list of common symptoms of depression. You may not have them all, but several usually develop:

• Core (key) symptoms:
  • Persistent sadness or low mood. This may be with or without weepiness.
  • Marked loss of interests or pleasure in activities, even for activities that you normally enjoy.
• Other common symptoms:
  • Disturbed sleep compared with your usual pattern. This may be difficulty in getting off to sleep, or waking early and being unable to get back to sleep. Sometimes it is sleeping too much (particularly in SAD - see below).
  • Change in appetite. This is often a poor appetite and weight loss. Sometimes the reverse happens with comfort eating and weight gain. (People with SAD often put on weight - see below.)
  • Fatigue (tiredness) or loss of energy.
  • Agitation or slowing of movements.
  • Poor concentration or indecisiveness. For example, you may find it difficult to read, work, etc. Even simple tasks can seem difficult.
  • Feelings of worthlessness, or excessive or inappropriate guilt.
  • Recurrent thoughts of death. This is not usually a fear of death, more a preoccupation with death and dying. For some people despairing thoughts such as "life's not worth living" or "I don't care if I don't wake up" are common. Sometimes these thoughts progress into thoughts and even plans for suicide.

Depression is different to the ups and downs from day-to-day that we all have. An episode of true depression is usually diagnosed if:

• You have at least five out of the above nine symptoms, with at least one of these a core symptom, and
• Symptoms cause you distress or impair your normal functioning, such as affecting your work performance, and
• Symptoms occur most of the time on most days and have lasted at least two weeks, and
• The symptoms are not due to a medication side-effect, or due to drug or alcohol misuse, or to a physical condition such as an underactive thyroid gland.

Many people with depression say that their symptoms are often worse first thing each day. Also, with depression, it is common to develop physical symptoms such as headaches, palpitations, chest pains, and general aches.

Some people consult a doctor at first because they have a physical symptom such as chest pains. They are concerned that they may have a physical problem such as a heart condition when it is actually due to depression. Depression is in fact quite a common cause of physical symptoms.

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

Some particular features of SAD

If you have SAD you tend to have some atypical (less typical) symptoms of depression. However, these do not occur in every case. Atypical symptoms are:

• 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.

SAD can markedly impair quality of life in winter. Symptoms tend to improve and go fairly quickly 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 low. 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 seasonal affective disorder and not the common form of depression?

The diagnosis of SAD is based on your 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 are more likely 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 emerges that you have the seasonal pattern of SAD.

What are the treatment options for seasonal affective disorder?

Light therapy

Research studies involving light therapy are difficult to interpret. This is because it is difficult to measure the real effect of improving symptoms with light versus the placebo effect. However, it is generally agreed by doctors that there is a good chance that light therapy can improve symptoms if you have SAD. However, light treatment takes time and commitment. See below for details.

Usual treatments for depression

The usual treatments for any kind of depression are also options to treat SAD. These include antidepressant medicines and various forms of psychological (talking) treatments such as cognitive-behavioural therapy (CBT). Regular exercise has also been shown to help ease symptoms of depression. For details of these usual treatments for depression see the leaflet called 'Depression'

Light therapy for seasonal affective disorder

What is light therapy?

This treatment consists of sitting in front of a special bright light for a session each day and/or using a dawn simulator. 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 light treatment involve?

Special light boxes are made for the purpose of treating SAD. There are various shapes and sizes. Perhaps the most commonly used one is a box about the size of a sheet of A4 paper that stands on a desk or table. Follow the instructions that come with the box. Basically:

• You start treatment in the autumn, as soon as symptoms begin. (Ideally, even before 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, in some people, evening sessions cause difficulty with sleeping afterwards.
• 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.

Some people use a dawn simulator instead of, or in addition to, a light box. Dawn simulators are devices that slowly increase the room light. They gradually come on in the early morning over a period of around 60-90 minutes at the time just prior to when you normally wake up. The light intensity from dawn simulators may not be as high as from light boxes so may not be as effective as a light box in relieving symptoms.

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?

Many people notice an improvement in symptoms within 3-4 days. If symptoms improve, they tend to 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 but it is thought that around 8 in 10 people with SAD improve with light therapy. See your doctor for other treatment options if you do not notice an improvement after six weeks.

Is light therapy safe?

There is a theoretical risk of damaging the retina (back of the eye). However, there do not seem to be any 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, aim get as much natural daylight as possible, especially at midday and on bright days. For example, if possible, go for a walk outside every day for 1-2 hours during the daytime as this may well improve symptoms. If you work indoors with artificial lighting, try to get out at lunchtime, even if it's raining. Perhaps go for a walk or eat lunch on a park bench if one is available.

For people who can afford it, a winter holiday to a sunny country will usually improve symptoms - but only for the duration of the time spent in the sunny country.

How can I get a light box or dawn simulator?

You cannot get a light box or dawn simulator on prescription from the NHS. Various companies make and sell them. The SAD Association (see below) provides 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.

Can seasonal affective disorder be prevented?

There is some evidence to suggest that a course of CBT or antidepressants taken before the winter arrives can prevent some cases of SAD. Further research is needed to confirm the place of these preventative treatments.

What is the outlook (prognosis)?

Around 6 in 10 people with SAD continue to have depressive symptoms each year in the long-term. However, as discussed above, you have a good chance of improving symptoms with treatment when symptoms develop. In about 2 in 10 people with SAD, the condition goes away completely after a few years and treatment is then no longer needed.

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 people with the condition.

References

• No authors listed; Management of seasonal affective disorder. Drug Ther Bull. 2009 Nov;47(11):128-32. [abstract]
• Lurie SJ, Gawinski B, Pierce D, et al; Seasonal affective disorder. Am Fam Physician. 2006 Nov 1;74(9):1521-4. [abstract]
• Evidence-based guidelines for treating depressive disorders with anti-depressants: a revision of the 2000 British Association for Psychopharmacology guidelines, British Association for Psychopharmacology (2008)