Each winter Annette Oakes was in the grip of a depression so black it took a cocktail of drugs to shake it off.

She had fallen victim to seasonal affective disorder (SAD) - a debilitating

condition in which the lack of sunlight leads to a severe case of the 'winter

blues'.

Today Annette is as full of life in January as in July thanks to a new hat

she wears twice a day which gives off roughly the same amount of light as a

clear spring morning, employing a technique known as light therapy.

Latest estimates are that one in five of the population is affected by SAD

each winter. Most cope, but many develop symptoms such as overeating,

lethargy and even joint pain.

There is mounting evidence that the condition can be controlled more

effectively and safely if patients are regularly exposed to bright light.

Nerve centres in the brain controlling rhythms and moods are stimulated by

light. At night, the pineal gland in the midbrain produces melatonin which

makes us drowsy.

At daybreak bright light causes production to stop. But on dull winter

days not enough light is received to trigger this waking up process. Other evidence points

to a link between exposure to light and the production of serotonin, a

neurotransmitter which dictates mood swings.

Now a

Cambridge firm called Outside In has modified the design into a

battery-powered cap that can be worn anywhere.

The cap - or visor - has two small bulbs that shine light directly to the

back of the eyes.

The bulbs are made from fluorescent tubing which emits a

light similar to natural sunshine.

Wired up to the visor is a pack which can be clipped on to a belt

containing rechargeable batteries.

Steve Hayes, director of Outside In, says the visor - which cost between

£150 and £240 each - has been selected by Nasa for use on space station

projects. Astronauts will wear the device to measure how it affects their

body clock in the absence of sunlight.

Annette Oakes says light therapy has transformed her winter existence.

'I used to feel like an animal in winter, wanting to burrow into the

ground and hide,' says the 63-year-old from Shipston-on-Stour, Warwickshire.

She used a light box and within 48 hours

her symptoms had disappeared.

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