Long nights, grey days – there is not much to love about winter. Christmas may bring a dash of festive cheer, but spring is still a long way off. So is winter making you properly depressed or just a bit blue? An annual dose of depression suggests that you may have seasonal affective disorder (Sad), a bona fide condition that was recognised even in ancient Greece. The physician Aretaeus of Cappadocia, writing in the second century, advised that “lethargics are to be laid in the light, and exposed to the rays of the sun (for the disease is gloom)”.

In 1984, the disease was rediscovered in 29 patients by Norman Rosenthal, a South African psychiatrist. Eleven of his depressed patients improved when treated with bright light. Sad is now included with major depressive disorders in the DSM-IV, a manual published by the American Psychiatric Association and used by doctors to diagnose mental health problems. It affects 6% of us, and is four times more common in women of childbearing age.

Many of the criteria for diagnosing Sad are the same as those for depression: low mood, lack of energy, inability to enjoy things, irritability and loss of interest in sex. But whereas depressed people can’t sleep and lose their appetites, up to 80% of those with Sad actually sleep and eat more. Sad people are usually affected at the start of autumn or winter and recover in spring (a rarer form affects people in summer). The condition gets more common as you move north up the east coast of America, but a similar association has not been found in Europe. So if you think you have it, what should you do?

The solution

The cause is uncertain but front-runners include disturbances in melatonin (the hormone that controls our pattern of sleeping and waking) that upset the circadian rhythm and levels of the “feelgood” hormone serotonin when there are fewer hours of daylight.

Although light boxes are often said to work by providing light (without harmful UV rays) for 30 minutes to an hour a day, the research evidence is not conclusive. This may not matter since any side-effects light boxes cause (headache, nausea, blurred vision) are mild and can be reversed by moving away from the light. But the respected Cochrane group, which provides analyses of research evidence, is not convinced that there is enough evidence to say light therapy, cognitive behavioural therapy or antidepressants work for Sad. This does not mean they don’t – just that the evidence is not of a high enough standard.

The Royal College of Psychiatrists strongly recommends spending as much time as possible outside in daylight during winter, with outdoor exercising being even better.

Discuss your symptoms with your doctor before you decide how best to tackle it. Sad may be a cute acronym, but it can be a serious condition.