No one looks forward to the shorter days after the clocks go back but for millions the sinking feeling isn't just gloom at the long nights ahead, writes Gabrielle Fagan.

Seasonal Affective Disorder (SAD), is a form of depression normally experienced in the winter months, which can affect sufferers so severely that their lives are disrupted.

SAD is four times more common in women and is characterised by sleep problems, overeating, lack of energy and emotional symptoms such as despair and anxiety and even loss of libido.

Iain Ryrie, Programme Director of Research at the Mental Health Foundation, says: "SAD has tended, until recently, to be a Cinderella diagnosis, in part because of the medical profession's concentration on clinical depression and the perceived association between SAD and the natural rhythms of life.

"One theory is that we are struggling against the seasonal variations of the globe. Partial hibernation or just slowing down in winter, which we were originally programmed to do, is rarely possible in today's busy Western lifestyle."

And he points out that Christmas preparations just add to the stress.

"Life tends be even more demanding mentally and physically with Christmas festivities looming.

"Put that together with light deprivation shorter days and longer nights known to impact on wellbeing and it's argued that those with an innate vulnerability to depression may be vulnerable to SAD."

He believes: "It's particularly important that we actively practise a healthy lifestyle at this time of the year. Good nutrition, exercise, exposure to natural light and plenty of rest all help to protect against seasonal depression and maintain mental well-being."

TREATMENT
Light therapy has been proved effective in up to 85 per cent of diagnosed cases. It involves spending up to four hours per day exposed to a light box' which is at least 10 times the intensity of domestic lighting.

Light boxes are not available on the NHS and cost between £100 and £400 from specialist retailers.

Try before buying several companies offer a home trial or hire scheme.

Anti-depressant drugs may be prescribed for people with severe SAD, although traditional antidepressants may increase feelings of sleepiness and lethargy. Newer drugs have been found to be more helpful and can be combined with light treatment.

Research among SAD sufferers has revealed that standardised extracts of the wild flowering herb St John's Wort, often referred to as the sunshine herb', may help relieve the symptoms when taken regularly.

The herb can interfere with some other conventional medication, so check with your doctor before taking it.