What could be more rational than feeling gloomy in January? It’s payback time
for over-extravagant Christmas shopping plus growing guilt as your various
resolutions begin to fail. Yet for five million or so people in the UK,
January, along with the other winter months, can usher in a particularly
intense form of gloom, withdrawal and depression, commonly known as SAD
(seasonal affective disorder). This fills them with an aching tiredness,
despair and a craving for precisely those foods outlawed by their
re-dedicated healthy-eating plans — carbohydrate-loaded bread, cakes,
biscuits and chocolate.
Everyone thinks that they know what causes it; shorter days leading to a lack
of sunlight, which, in turn, lead to the body producing too much of the
sleep hormone melatonin. Increased amounts of this hormone is what is
believed to fill you with an urge to burrow back under the bedclothes as
often as possible.
Lack of sunlight is also believed to result in lower levels of the hormone
serotonin, which is meant to counter depression. It’s a neat
scientific-sounding explanation that even comes with a logical treatment: 20
minutes or so exposure to bright full-spectrum light to replace what’s been
missing.
But a Body&Soul-supported event on Tuesday will explore some of the
complexities behind that apparent simple solution. A debate on winter blues,
at the Science Museum’s Dana Centre, will discuss how light can reset your
hormones, raising antidepressant serotonin levels and reducing
sleep-inducing melatonin. But there should also be plenty of surprises in
store because a radical new view of SAD has emerged recently.
Light boosts serotonin? Not necessarily. You’re sleepy because of extra
melatonin? Maybe not. Even more controversially, it might not be the lack of
light in winter that’s changing your mood. The real reason for SAD could be
that it’s a once-valuable evolutionary adaptation that prepares women for
pregnancy.
The key to this new theory is that though SAD responds to some treatments for
regular depression, there are crucial differences between them and these
point the way to a new understanding. Normally if you have depression you go
off food rather than having cravings and, far from sleeping all the time,
you’re more likely to be an insomniac. Most striking, though, is the
male-female difference. While women are twice as susceptible to normal
depression as men, they are four times more likely to suffer from SAD.
What’s more, while regular depression worsens with age, the seasonal
disorder seems to improve after the menopause.
These features have led to a revolutionary new viewpoint on the condition.
What it all suggests, according to two Canadian researchers in last month’s Journal
of Affective Disorders, is that SAD is actually an evolutionary response
in women to the fact that, historically, winter has been the best time to
become pregnant. Food cravings, social withdrawal and a need to rest are all
features of pregnancy. And spring and early summer, when food becomes more
plentiful, was historically the best time to give birth.
This fits in well with an even more radical perspective on the disorder, put
forward by one of the main speakers at the Body&Soul-DANA event, who
sees it as part of a great rhythm that affects nearly all living beings.
“Virtually all animals and plants, even in the Tropics, have strong annual
rhythms of reproduction and re- generation,” says Dr Gerald Lincoln, of the
human reproductive sciences unit, at Edinburgh University. “The apparent
slowing down and withdrawing in the winter isn’t a special state: it’s the
system free-running.”
Research on sheep shows that what sets the clock of their annual cycle is the
arrival of longer days of spring, not darker winter. “When you sit in front
of a light box, you’re not making up for low winter light but shifting your
annual rhythm into the more active summer phase. We don’t understand what
the longer-term effects of that might be,” he says.
So it looks as though SAD is just one of the penalties we pay for a lifestyle
that is both round the clock and round the year, like jet lag and
night-shift sickness. Winter blues might be the result of misinterpreting a
natural physical slowdown. The problem is not that you’re depressed but that
you are still trying to function at your summer speed.
None of this is to deny that SAD makes winter a misery for millions, or that
light boxes seem to help many, or that once you recognise the pattern other
effective treatments are also available. A number of trials have shown that
about 20 minutes in the morning in front of a light- box pumping out light
at an intensity of 10,000 lux significantly helps about 60 per cent of
sufferers; the lux level in an office on a winter’s afternoon might not even
reach 500.
Mainstream medicine, more used to treating psychological disorders with
antidepressants, remains sceptical about SAD as a distinct condition. “A few
GPs do provide light boxes but most are still suspicious and regard it as
some sort of mumbo-jumbo,” says another speaker at the Body&Soul-DANA
debate, Professor Anne Farmer of the Institute of Psychiatry in London.
“Employers might also think that you were pretty cranky if you tried to bring
one into the office. But if it was available on the NHS, it would be very
cost-effective.”
Another form of treatment that has just been shown to be as effective as both
light and regular antidepressants is CBT (cognitive behavioural therapy).
“Not everybody can fit in half an hour or so every morning just sitting
bathed in light,” says Dr Kelly Rohan, a psychologist at the University of
Vermont, who conducted research comparing light therapy, CBT and Prozac.
“That’s why a lot of people stop it. The timing of CBT is more flexible.”
Her study found that the effects of CBT were also longer lasting; only 6 per
cent of those who had had the therapy were depressed a year later, compared
with 40 per cent of those who had received light treatment.
The experts also recommend exercise. Rohan points out that a walk on an
overcast winter’s day could expose you to 10,000 lux.
Professor Farmer advises her patients to set up an exercise routine in the
summer, making it easier to continue in the winter. Supplements and a change
of diet may also help, although full-scale trials haven’t been done.
SAD facts
- In some women, there seems to be a genetic link between susceptibility to
bulimia and susceptibility to SAD (seasonal affective disorder).
- SAD may be linked to flare-ups of inflammatory conditions such as arthritis.
The rise in melatonin driven by less light could shift the immune system
into a more inflammatory state.
- SAD has a noticeable effect on the stock market. Research has indicated that
people make less risky investment decisions in the winter.
- Reduced sunlight raises the risk of vitamin-D deficiency, which is linked with
depression. Some researchers believe that 90 per cent of people in
Britain could be vitamin D-deficient.
