A café designed to help people beat the winter blues by giving them a much-needed dose of light has been set up at the Science Museum in London.
The cafe offers intense exposure to light
The Dana Café offers free 20-minute light treatments to counter the effect of dark winter days.
Up to 500,000 people, the majority women, are thought to suffer from SAD - seasonal affective disorder.
The condition, more common in northerly latitudes, can cause symptoms ranging from low spirits to severe depression.
SAD is not fully understood, but is thought to be linked to a biochemical imbalance in an area of the brain called the hypothalamus, which controls mood, appetite, and sleep.
It is thought to be caused by the shortening of daylight hours and lack of sunlight in winter.
Symptoms can include sleep problems, lethargy, overeating, anxiety, loss of libido and mood swings.
There is some evidence the condition runs in families.
And up to one in eight people in the UK are thought to experience a milder form of the condition, known as sub-syndromal SAD.
Light triggers changes
Exposure to bright light for between one and four hours a day can be an effective treatment for SAD in up to 90% of cases.
It is thought that light triggers a change in chemical production within the brain, raising levels of the mood chemical serotonin, and slowing production of the hormone melatonin, which is responsible for making us sleepy and animals hibernate.
However, only bright light has any beneficial effect.
The Dana Café Light Lounge contains four specially designed light boxes, each of which produces light more than five times brighter than normal house lights.
The atmosphere is designed to be relaxing, with the light boxes arranged around a circular sofa.
Kat Nilsson, Dana Centre programmes manager, said: "We wanted to offer people who may be suffering from SAD the chance to test out one of the most popular treatments available."
Jennifer Eastwood, a founder of the SAD Association, said the idea had been pioneered in the Scandinavian countries, where rates of the condition are highest.
She said: "I'm surprised this has not caught on more in this country."