“Winter is coming” – Ned Stark, Game of Thrones

Why do some people get SAD in winter?

It may be sultry...but winter is on its way. And as the days draw in, seasonal affective disorder (SAD) raises its disconsolate head.

What is SAD?

SAD, in essence, it is a form of winter depression, the symptoms of which may include:

  • Lethargy, a lack of energy, feeling unable to carry out normal tasks
  • Sleep problems, finding it hard to stay awake during the day, but having trouble sleeping properly
  • Loss of libido
  • Anxiety or an inability to cope
  • Social problems and irritability: a general loss of interest in everyday activities
  • Depression, feelings of gloom and despondency for no apparent reason and a persistently low mood
  • Craving for carbohydrates and sweet foods, leading to weight gain.

You should consider seeing your GP if you think you might have SAD and you're struggling to cope. Your GP can carry out an assessment to check your mental health. They may ask you about your mood, lifestyle, eating habits and sleeping patterns, plus any seasonal changes in your thoughts and behaviour.

Why do people get SAD - and who gets it?

It's not fully understand what causes SAD, but the reduced amount of sunlight in winter seems to be important. It's thought that a lack of sunlight might stop the hypothalamus (part of the brain) working properly which, in turn, may affect the:

  • Production of melatonin, a hormone that makes you feel sleepy; in people with SAD, the body may produce it in higher than normal levels
  • Production of serotonin, a hormone that affects your mood, appetite and sleep; a lack of sunlight may lead to lower serotonin levels, which is linked to feelings of depression (see below)
  • Body's internal clock (circadian rhythm): lower light levels during the winter may disrupt your body clock and lead to symptoms of SAD.

It's also possible that some people are more vulnerable to SAD as a result of their genes, as some cases appear to run in families. People living in very northern areas do not appear to suffer more SAD than people living further south, so other factors may also be important.

Research has shown that seasonal affective disorder (SAD) symptoms in the winter are associated with an increase in cerebral serotonin transporter (SERT) binding (or something that increases the binding of serotonin to a protein that transports serotonin around the brain). A new study found that people who were resilient to SAD "downregulated" their levels of the serotonin transporter during the winter. These findings offer good grounds for treatment of SAD with selective serotonin reuptake inhibitors (SSRIs) - a form of antidepressant.

SAD is most common in women during the years when they can have children. It's about three times more common in women than it is in men. SAD is less common in children and, in older adults, it affects men and women equally.

In the UK, about three people in every 100 have significant winter depression.

How is SAD treated?

The main treatments are:

  • Lifestyle measures – including getting as much natural sunlight as possible, exercising regularly and managing your stress levels
  • Light therapy – where a special lamp called a light box is used to simulate exposure to sunlight
  • Talking therapies – such as cognitive behavioural therapy (CBT) or counselling
  • Antidepressant medication – such as selective serotonin reuptake inhibitors (SSRIs) - as mentioned above.