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Season Affective Disorder

Seasonal Affective Disorder (SAD) is a type of depression or mood disorder with a seasonal pattern.

The most common form of SAD is also called winter depression or winter blues, because symptoms are worst in the winter months. They tend to start from around September, are worse when the days are shortest (in December, January and February) and improve in the spring.

There is also a summer version of seasonal affective disorder, but this is far less common and has different symptoms. Around 1 in 50 people in the UK have SAD. It is more common in women than in men and most commonly starts between the ages of 18 and 40.

Up to 1 in 8 people in the UK experience milder symptoms of winter 'blues' (sub-syndromal SAD). Studies around the world have shown that SAD becomes more common the further you are away from the equator. This suggests that SAD is linked to the change in the number of daylight hours through the year.

Symptoms

SAD can be a disabling illness. Without treatment, people with SAD can find it difficult to live a normal life. Sub-syndromal SAD or 'winter blues' is a milder condition, but it can still have a major effect on how people feel and act. Symptoms of SAD include:

  • Sleep problems such as disturbed sleep at night, sleeping for longer, and feeling sleeping during the day;
  • Feeling tired and lacking in energy;
  • Increased appetite, particularly craving carbohydrates and sweet foods, and weight gain;
  • Feeling generally low and having mood swings;
  • Not feeling sociable or wanting to go out with your friends;
  • Decreased sex drive;
  • Difficulty concentrating; and
  • Loss of interest in work and hobbies that you previously found enjoyable.

People with severe symptoms of SAD may also have:

  • Feelings of depression, hopelessness, or despair; and
  • Stress and anxiety.

A small number of people also experience a short period of hyperactivity in the spring.

Causes

The cause of SAD is not fully understood, but is thought to be linked to reduced exposure to light during the winter months. Researchers have shown that bright light makes a difference to brain chemistry, but it is not clear exactly what the effect is. 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 prevents the hypothalamus from working properly. Melatonin, a sleep-related hormone released in the brain, has also been linked to SAD. This hormone is thought to cause symptoms of depression and is produced at increased levels in the dark. SAD may also have a genetic cause. It has been shown that you are more likely to develop SAD if you have a close relative who has it.

Diagnosis

It can sometimes be quite difficult to tell the difference between SAD and other types of depression. It may not be immediately obvious that the symptoms are linked to changes in the seasons, as people with non-seasonal depression can also have repeated cycles of symptoms worsening and improving, but for different reasons.

It is therefore important to try to spot the pattern of symptoms always appearing in the winter months, and disappearing in the summer on their own, not as a result of treatment. It usually takes at least two years to show this pattern clearly. A special questionnaire called the Seasonal Health Questionnaire is sometimes used to help specialists work out whether a person has SAD.

Treatment

Research has shown that light therapy can be an effective treatment for SAD. It involves daily exposure to bright light, for periods between 1 and 4 hours. A specially designed light box is used to produce light that is similar to daylight, and much stronger than the light from a normal light bulb. It needs to be set at a strength of at least 2500 lux to be effective. Lux is a measure of the intensity or brightness of light, and a normal light bulb is around 200-500 lux, so a light box is much brighter.

Light treatment should be used daily in winter starting when the first symptoms appear. Symptoms usually improve within a few days of starting the treatment and this continues if the light box is used daily. Light equipment to use at home can be bought privately, and includes light boxes, portable light visors and bedside lights that simulate sunrise. Light treatment is not available on the NHS, but any treatment for SAD should be supervised by your GP or an NHS clinic that specialises in the condition.

Anti-depressant drugs are sometimes diagnosed to help treat SAD. Selective serotonin re-uptake inhibitors (SSRIs) seem to be the most effective in easing the depressive symptoms of SAD, especially in combination with light therapy. Talking therapies such as psychotherapy, counselling or cognitive behavioural therapy (CBT) may also help some people to cope with SAD.

Complementary therapies that have a relaxing effect, such as massage and acupuncture, may also be helpful. The herbal remedy St John's Wort is thought to be helpful in relieving some of the symptoms of SAD but you should always consult your GP or pharmacist before taking it, as it can interfere with other drugs such as the contraceptive pill. Self-help measures for SAD include:

  • During the day, spend as much time as possible outdoors. Even a quick lunchtime walk can be beneficial.
  • Take regular exercise, particularly outdoors in daylight if possible.
  • Plan ahead so that you don't have lots of things to do during the winter. Leave any major projects until spring or summer.
  • Try decorating your home in light colours and spend plenty of time near windows, to make the most of natural light.
  • Going on holidays to somewhere sunny during the winter months can help, but you may feel worse when you come home and it is still cold and dark.
  • Talk to your friends and relatives, so that they understand why you feel down and irritable during the winter, and this will help them to support you.

The information shown here is Crown copyright and has been reproduced with the permission of NHS Direct. Last updated June 2007.