As acronyms go, SAD is among the catchiest - but would the condition be less talked about if its name was just 'winter blues'?
That was the term South African psychiatrist Norman Rosenthal first came up with, after discovering that he himself was a sufferer. Emigrating to New York in the late 1970s, one gray November day, he was suddenly struck down with lassitude and depression. This mood lasted until spring, when he became his old self again, with his usual energy fully restored.
Rosenthal re-coined his condition 'seasonal affective disorder'-or SAD-and was quick to establish what caused it. It wasn't the low temperatures, miserable weather or denial of outdoor exercise found in winter, but simply the lack of sunshine. People in sunny Florida didn't get it whereas, in New Hampshire, 10 per cent of the popula-tion were routinely affected. Similarly, in Europe, the UK's SAD rate of 5 per cent is about half that of Finland.
We now know quite a lot about SAD. It's four times more common in wo-men than men, but if men are affected, the symptoms are liable to be worse. Indeed, in some men, SAD can morph into severe clinical depression. It is rarer in the old than the young. People from southern latitudes who move north may have an increased risk of SAD compared with natives-for example, native Icelanders who emi-grate to Canada have less SAD than other non-native Canadians.
But as for how SAD arises, there is a range of theories. The three main ones are: circadian phase-shifting; abnormal pineal-melatonin secretion; and abnor-mal serotonin synthesis. The evidence is equivocal for all three.
While clinicians may argue about the causes of SAD, therapists agree that there's basically one treatment option: give the SAD patient what he's lacking with the use of artificial light.
Initially, psychiatrists medicalized the treatment by making patients sit for hours in front of a bank of electric lights in a hospital or clinic. But it didn't take long before someone had the bright idea of letting SAD people do it at home. At the same time, powerful lighting options became available.
Light treatment for SAD is probably the simplest and least controversial treatment in psychiatry. There's now no doubt that it works. The only arguments concern how much, when and what type of light.
A major review of the evidence was carried out last year by Dr Alan Miller of Thorne Research Inc, the respected alternative-medicine research group. "Light therapy has been shown in numerous patient populations to be an effective method of treatment of SAD," he says. "It has an overall positive treatment response of up to 70 per cent, with rarely any side-effects" (Altern Med Rev, 2005; 10: 5-13).
And what about the fine-tuning issues?
- Light levels. The evidence seems to show that two hours in front of a modestly bright light (2500 lux) is as good as 30 minutes in front of a seriously bright one (10,000 lux).
- Best time of day. Although the circadian/melatonin theories sug-gest that morning ought to be better, in practice, it apparently makes no difference. Morning or evening doses are just as effective, although a combination of the two is better still.
- Type of light. Although full-spectrum (artificial daylight) lighting is known to improve moods and efficiency in offices or schools, for SAD people, it seems to make no difference-any kind of white light will do. The only exception was the somewhat obvious conclusion of a Swiss study, which showed that 30 minutes of artificial light therapy wasn't as effective as an hour's walk in the Swiss mountains.
Although the weight of evidence shows that it's not so much the timing, but quantity, of light therapy that's important, one study has shown that "dawn simulation" may actually be better. This procedure involves gradually raising light levels from
4.30 am to 6 am. The final light levels are relatively low, peaking at 250 lux-equivalent to sunrise on a hazy day (Biol Psychiatry, 2001; 50: 205-16).
Non-drug medications have also been found to help. Melatonin (2 mg at night) will improve, if not the SAD itself, at least the "quality of sleep and vitality" (Eur Neuropsychopharmacol, 2003; 13: 137-45). L-Tryptophan (2 g/day) may alleviate the depression in SAD people who fail to respond to light therapy (Can J Psychiatry, 1997; 42: 303-6), as can St John's wort (900 mg/day) (Pharmaco-psychiatry, 1997; 30: 89-93).
Another option is a high-density (2.7 3 106 ions/cm3) negative ionizer (J Altern Complement Med, 1995; 1: 87-92).
SAD symptoms in winter
- Standard symptoms of depression (lethargy, fatigue, anxiety, inability to cope, social avoidance)
- Increased appetite, especially for carbohydrates
- Increased sleep
- Loss of libido
- Heaviness in the limbs ('leaden paralysis')
- Craving for carbohydrates and sweet foods