(Extract from the Mind Publication "Understanding Seasonal Affective Disorder ")

'For years I suffered from depression. It started in the autumn, as the evenings drew in. By Christmas I would be so low I could barely get out of bed. I couldn't cope with organising the celebrations, so we used to go to my mother-in-law's. One year I felt so bad that I went to bed on Christmas Eve and refused to move ... That's what made me realise there was something seriously wrong.'

Rita Carter, Healthfront in 'Daily Telegraph'  22.10.94

Seasonal affective disorder (SAD), or 'winter depression', may affect as many as a third of us, but the problem often goes undiagnosed. for a smaller number, it can be seriously disabling. This booklet is for anyone who wants to know how seasonal changes in light levels affect behaviour or mood, and what can be done about it.

Why do we have seasonal mood changes?

Most of us feel better when the sun is shining - more cheerful and energetic. On grey, gloomy days, especially in winter, we tend to feel less enthusiastic, more inclined to stay indoors, or even in bed, to do less work, to socialise less and eat more. The reason for this is the change in the quality and quantity of light. As winter approaches, there are fewer daylight hours and so, by December, we often get up in the dark and come home from work or school in darkness. What's more, the shorter winter days don't have the same light intensity that we get in summer.

The cycle of light and dark determines our sleeping and waking patterns. Until the widespread use of electric light, people used to wake and get up with the dawn light and sleep longer and be less active. Nowadays, we tend to override these natural rhythms and manipulate the hours of light and darkness to suit our sophisticated lifestyle. Many night-shift workers and jet-lagged air travellers suffer from disrupting their body clicks in this way.

The effects of light

Some people seem to be more affected than others by lack of daylight. when light hits the back of the eye (the retina), messages are passed to the part of the brain (the hypothalamus) that rules sleep, appetite, sex drive, temperature, mood and activity. If there's not enough light, these functions are likely to slow down and gradually stop, like a car that is running out of fuel. Some people seem to need a lot more light than others to keep them on the road, and these are the people who develop seasonal affective disorder (SAD), to a greater or lesser extent.

What are the effects of SAD?

People with SAD experience seasonal changes of mood and behaviour. The most common mood change is depression, a so-called affective disorder. Symptoms may start emerging between September and November and continue until March, April or even May.

Around 20 per cent of cases are fairly mild, and are known as the 'winter blues', or sub-syndromal SAD, occurring mainly during December, January and February. But between two and five per cent of cases have severe SAD and can't function in winter without continuous treatment. Many find it difficult to study or hold down a job during this season, because they feel lethargic or sleepy and find it difficult to concentrate. Their relationships are put under strain, and even break up, because they become irritable, unloving and so less lovable.

Nine out of ten people report that they eat and sleep more in winter and that long streches of grey skies make them more down in the dumps. This is all perfectly natural. But for those with SAD, the symptoms are more severe, and happen regularly, each winter, following a seasonal pattern. The symptoms go away in spring, either suddenly (with a short period of hyperactivity) or gradually, depending on the amount of sunlight in the spring and early summer.

Unfortunately, SAD is often misdiagnosed or overlooked. Once someone has experienced two or three winters of symptoms, they can be said to e suffering from SAD. The symptoms are many and varied, and people can experience any of the following common effects:

• Lethargy or fatigue: lacking in energy and being unable to carry out your normal daily routine.
• Sleep problems: oversleeping, finding it hard to stay awake during the day, sometimes having disturbed nights and early morning waking.
• Depression (including postnatal depression): feeling sad, low, weepy, guilty, afailure; sometimes hopeless and despairing, sometimes apathetic and feeling nothing.
• Mood changes: in some people, bursts of overactivity ad cheerfulness (known as hypomania) in spring and autumn.
• Overeating: craving carbohydrates and putting on weight (which may increase negative feelings).
• Bulimia: eating large amounts of food and then vomiting.
• Social problems: irritability (especially among children), and not wanting to see people; abusive behaviour.
• Concentration problems: difficulty 'thinking straight', making decisions or concentrating.
• Anxiety: tenseness and inability to cope with everyday stresses; panic attacks.
• Loss of libido: not being interested in sex or physical contact.
• Alcohol and drug abuse.
• Feeling under the weather. Most people with SAD have a lowered immune system during the winter, and are more likely to get constant colds, infections and other illnesses.
• Period problems.

The symptoms of the 'winter blues' (sub-syndromal SAD), the milder version, are similar but they are less severe and last for a shorter period that full-blown SAD. Typically, they might include tiredness, lethargy, sleeping and eating problems.

Topics also included in this leaflet are: