THE news that it’s women, but not men, who experience greater seasonal changes in their mood across the year, including more depressive symptoms in winter, has highlighted the much misunderstood illness known as Seasonal Affective Disorder (SAD).

A new study from the University of Glasgow has found these changes appear to be independent of social and lifestyle factors, such as smoking, alcohol use and physical activity.

The research, from the University’s Institute of Health and Wellbeing and published in the Journal of Affective Disorders, showed low mood, tiredness and anhedonia (the inability to experience pleasure from activities usually found enjoyable) peaked in the winter months in women. A relationship between shorter days and greater depressive symptoms in women was also found, but this may have been explained by variation in outdoor temperatures.

The condition known as SAD (clinically-significant depressive symptoms peaking during winter months) affects up to three per cent of the general population. It is also more common for patients with a history of major depression to experience more symptoms during winter, with new prescriptions of antidepressants also rising.

The researchers performed a cross-sectional analysis of more than 150,000 participants of the UK Biobank cohort, and analysed data to assess evidence of seasonal variation by scoring ‘total depressive symptoms’, plus symptoms of low mood, anhedonia, tenseness and tiredness. Associations between depressive symptoms and day length and average outdoor temperatures were also assessed.

Daniel Smith, Professor of Psychiatry, said: “This very large, population-based study provides evidence of seasonal variations in depressive symptoms which appear to be more pronounced in women than in men.

“We don’t yet fully understand why this should be the case, but it was interesting that the changes were independent of social and lifestyle factors, perhaps suggesting a sex-specific biological mechanism. Clearly, this is a complex but important area which requires further study.

“Clinicians should be aware of these population-level sex differences in seasonal mood variation, to aid the recognition and treatment of depressive symptoms across the calendar year.”

While a touch of winter blues is quite common, full-blown SAD is relatively rare and can be majorly debilitating. More than just grumpiness at the weather, SAD it has been recognised as a form of ‘seasonal depression’ by the NHS, which estimates there are around two million people in the UK with the condition, which can cause “low mood and a lack of interest in life”.

“Depression and SAD are very physical conditions, although people don’t understand that because they can’t see it,” said Dr Peter Saul of the Health Centre in Rhos, near Wrexham

“There is an actual chemical change involved in the brain and the ‘winter blues’ have to do with people not being able to get out as much, enjoying the activities they’d normally get involved with during the summer, the low temperature and the higher likelihood of being ill with colds.”

“No-one knows exactly what causes SAD but the theory is that it has to do with the levels of light people are exposed to.”

The skin, Dr Saul explained, is the single largest organ in the body.

He said: “People forget how influential it is – and that it is derived from the same embryonic tissue that also develops into our nervous system.

“Exposure to sun releases some neural hormones which help stabilise mood. Some are more sensitive to this than others. By extension, if you don’t get enough sunlight, your mood can drop thanks to underproduction of a hormone called serotonin.”

Just like everything else that is supposed to be good for you – eating well, getting exercise and plenty of sleep – seeking sunlight is easier said than done for some people. Our lifestyles have changed radically in the previous century, with manual outdoor jobs disappearing to be replaced by deskbound office jobs, where the seasons and length of day have nothing to do with the length of shifts.

Dr Saul said: “I have seen examples of people who have SAD although I’d say that, unless you are experiencing severe depression, your surgery should not be your first option.

“If someone is feeling down and suspects they may have seasonal affective disorder, there are a number of things they can do themselves.

“The first is to get out and about more. If they have the money, then go abroad. If you don’t, you can always look into the light box option.”

One of Dr Saul’s patients opted for a light box, which emits a high lux count (lux is a unit of luminance).

He said: “It seemed to work well for her.

“You can find them online, though I’d make sure you get one that’s powerful enough.”

“Exercise is good for generating endorphins which help with depression-like symptoms and family members can also help by understanding that the person with SAD can’t help the way they feel – any more than someone can help when they are suffering from diabetes or epilepsy.

“It’s something they have to manage.”