Seasonal affective disorder (winter depression)

Health and Nutrition > Diseases > W Reviewed by Dr John Powell, MRCPsych specialist registrar

What is seasonal affective disorder (winter depression)?

The terms 'winter depression' and seasonal affective disorder (SAD) describe a form of depression that occurs in the winter months. Women are affected more often than men, and the prominent symptoms are:

- low mood starting in autumn or winter.
- lack of energy.
- irritability.
- overeating and weight gain (there is often a craving for carbohydrate food).
- lack of interest in socialising.
- increased sleep and daytime sleepiness.

Opinion is divided as to whether this is a separate disease from other forms of depression, although there does appear to be a group of people that suffer with it on a regular basis starting in the autumn or winter and then recovering in the spring or summer.

It is unusual for these symptoms to be of sufficient severity for them to be brought to the attention of doctors but for those individuals who do find that they need medical help, all the usual medication and psychological treatments may be tried. There have also been reports of successful treatment using exposure to bright light.

There is a small proportion of people with regular winter depression who find that their mood does not simply return to normal in the spring/summer, but that it becomes excessively high. It is possible that these individuals have a seasonal bipolar affective disorder (seasonal manic depression) and again the mood stabilising treatments for the more common non-seasonal form of the illness are available.

What causes winter depression?

In some people the apparent relationship to the seasons is simply because of stresses and difficulties that regularly happen for them at that time of year. The illness these people suffer from would seem to be little different to any depressive illness that is triggered by a stressful event.

Where a regular precipitating event does not occur, the cause is not known. It is possibly related to the reduction in natural light and the lower temperatures in the winter months but this is uncertain and there is no good evidence for it being more common in very northern countries where the winter hours of daylight are much shorter.

It has been suggested that the release of a brain chemical (melatonin) may be involved. Melatonin release is influenced by exposure to light and can exert an effect on several bodily rhythms, but research into this has been fairly inconclusive.

How is it treated?

When treatment is necessary it may include:

- antidepressant medication
- psychological therapy
- bright light therapy.

Bright light therapy consists of the sufferer having a special lamp or light box at home that provides a very strong source of light.

Light therapy has certainly been found to help some people with SAD, and has been reported to reduce the depressive symptoms after just a few days. The symptoms are also reported to return quite quickly after the treatment is stopped.

The sufferer needs to be exposed to the light source for a number of hours each day, and the beneficial effect appears to be due to the light rather than the fact that the person's sleep is reduced with the treatment. It is difficult, however, to be sure that the benefit is not a 'placebo effect', especially as there is little evidence for an alteration in the level of melatonin as a result of the treatment.

Light boxes are made by Bright Spark (5000 lux box) and Philips (HF305 Bright Light Energy light bath 10,000 lux), and can be ordered from any Boots store. If you provide a signed statement confirming you have SAD, you will not be required to pay VAT. And if you live in London, you can use Philips light baths simply by visiting the Bright Light Café at Konditor & Cook, 66 The Cut, Waterloo, London, SE1.

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