What are the symptoms of seasonal affective disorder? Is it a real complaint? Neil Casey, Cambridge

Seasonal affective disorder (SAD) has all the standard symptoms of depression. Perhaps of all these symptoms the most important one is the feeling of absolute hopelessness - life has so lost its point that nothing seems worth doing. All pleasure has disappeared from activities which in the past meant so much to you.

Apart from the standard and almost invariable symptoms there are many other very important changes. A patient who is depressed usually finds that it is reasonably easy to get off to sleep, but wakes very soon - sometimes within an hour or two and then lies awake until it is almost time to get up. When they get up they can only drag themselves around during the course of the day, although their mood usually picks up so that someone who has been in the depths of despair in the early morning is not as depressed and dejected as they were at breakfast time by afternoon. There is usually a loss of appetite, and a consequential loss of weight – nearly all people who are depressed have lost half a stone in weight. Libido, as well as appetite, disappears. In general, life hardly seems worth living and, indeed, there is always the constant worry of a suicide attempt.

How do the symptoms of SAD differ from those of standard depressive illnesses? SAD is diagnosed only if a patient has suffered from it in three different years - not necessarily consecutive. The symptoms must last for a 60-day period at about the same time in the autumn or winter, and once the lighter evenings have returned and the weather is not so miserable they should disappear. It is essentially a matter of light deprivation.

The other difference may be that instead of the patient being insomniac they are hypersomniac. That is to say, they take to their beds like a dormouse and can stir themselves only for a short time each day – usually about teatime. This is not an invariable symptom, and most people with SAD have the pattern of depressive insomnia. This particular variant on sleep disturbance just happens to be a little bit more common than in patients with other forms of depression.

Also nearly all depressed patients eat less and lose weight, while some patients with SAD eat more and put on weight - another reason why it used sometimes to be called the "dormouse syndrome". Many patients who are depressed do not like moving outside their own house and become holed up within it. This too, again like the dormouse, is more common in SAD sufferers. The loss of libido seems to be more complete than in other forms of depression, and the mood swings within the depressed state may be more marked.

SAD is a real complaint, although there are some psychiatrists who think that in depressed patients there is usually an exacerbation of their symptoms in the winter and this is merely an exaggeration of their state. We think it is a real complaint, because providing a powerful light source so that the days are artificially lengthened can relieve symptoms.

Is there any evidence that prescription antidepressants work better than St John's wort? Also, has any research been done into the use of food colourings to "kick start" somebody suffering depression? Colours such as tartrazine and sunset yellow that cause hyperactivity in children seem to work well in overcoming the lethargy associated with depression. Jeremy Bushell, Exeter

Yes it is very important to be aware that St John’s wort has shown to be effective in treating mild depression or, at the very worst, mild/moderate depression. St John’s wort isn’t effective at treating a major depressive state.

I don’t believe that any research has been done into the use of food colourings as a means of treating depression, but the concept is similar to that which used to suggest that a small dose of amphetamine for a few days was one method of treatment. This turned out to be very faulty thinking. Once the amphetamine effect had worn off the patient was left more depressed than before. Furthermore, when treating depressed patients it may, in some cases, be possible to induce an addictive state. One of the valuable points about antidepressants is that they don’t cause that form of addiction.

Is there any substantial evidence of the benefits of taking antioxidant tablets as a supplement to a healthy diet and lifestyle? Philippe Gogniat, Blonay, Switzerland

There is absolutely no doubt that antioxidants are an essential part of any healthy diet, and a good lifestyle depends on them. What is not certain is whether the antioxidant tablets always contain the essential chemical which gives rise to these advantages. Antioxidants are available in many foodstuffs and, in particular, in bright coloured vegetables and fruits and their juices, including red wine. The general view, which I share, is that it is probable that antioxidant tablets do contain at least some of the essential features which would be obtainable in nature. It is not only antioxidant vitamins which are useful, but also antioxidant minerals and other trace elements. There is evidence that selenium is useful. There is also evidence that lycopene has great value in preventing several cancers, including cancer of the prostate and breast cancer. Selenium is useful, so far as prostate cancer is concerned, and many people take vitamin C and E. Folic acid has its obvious uses both in preventing heart diseases and some forms of foetal abnormality. Stick to your healthy diet and half an hour’s brisk exercise a day, but to be on the safe side – belt and braces - I should also take a good-quality multivitamin and mineral tablet.

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