What is Seasonal Affective Disorder (SAD)?

Seasonal Affective Disorder (SAD) is a type of depression which comes and goes according to seasonal changes.  Typically, SAD affects people in the cold, dark winter months, predominantly during December, January and February.  Whilst SAD is very rare in those who live near the equator where sunlight levels tend to remain high throughout the year, in the UK it’s estimated that around one in 15 people experience symptoms.

What causes SAD?

The exact cause of SAD remains unclear, although most research suggests the disorder is a result of reduced exposure to sunlight during the winter months.  The general assumption is that the change in the weather affects an area of the brain called the hypothalamus; a significant role of the hypothalamus is linking the body’s nervous system to the endocrine system. In the case of SAD, it’s generally understood that SAD stops the hypothalamus from functioning properly, particularly affecting:

  • Melatonin levels. Melatonin is a hormone that makes you feel lethargic – people who have SAD may produce more melatonin than is usual
  • Serotonin levels. Serotonin is a hormone that affects your mood, appetite and sleep.  A lack of exposure to sunlight can result in lower serotonin levels than normal, which is linked to feelings of depression
  • Your body’s internal clock. Your internal clock (circadian rhythm) uses sunlight to time various bodily functions, such as when you wake up in the morning.  Lower levels of natural sunlight in the winter can affect your internal clock and result in symptoms of SAD

What are the symptoms of SAD?

For many people, SAD can have a huge impact on their day-to-day lives.  Common symptoms tend to include:

  • Irritability
  • Sleeping for longer than usual
  • Having trouble getting up in the morning
  • Feelings of despair and worthlessness
  • A persistent low mood
  • Anxiety
  • Weakened immune system
  • Craving carbohydrates and gaining weight
  • A lack of energy and feeling sleepy during the day

Is there a cure for SAD?

There is no quick-fix for SAD, however your GP will be able to offer treatments which are suitable for you.  Depending on the severity of the disorder, these may include:

  • Lifestyle changes, such as exercise, managing stress and getting as much natural sunlight as you can
  • SAD light box therapy, where a special lamp is used to simulate exposure to sunlight
  • Therapies such as cognitive behavioural therapy or counselling
  • Medication, such as antidepressants or selective serotonin reuptake inhibitors (SSRIs)