Seasonal Affective Disorder

Seasonal Affective Disorder

Seasonal Affective Disorder (SAD) is a type of depression triggered by lack of light in winter. In the *UK 7% of the population suffer from SAD, with a further 17% getting a milder form of the condition, commonly known as the winter blues or winter depression.

SAD starts as the days get shorter, with the loss of natural daylight triggering depressive symptoms such as lethargy, sleep problems and less interest in sex.

What causes SAD?

One key role of light is to synchronise our body clock to the 24 hour day but SAD sufferers require a higher light intensity to do this. In the winter, when light levels are lower, they produce too much melatonin (the hormone which helps us sleep) and less of the “feel-good” hormone serotonin. As a result people with SAD feel sleepy and depressed.

The latest thinking is that the disorder has genetic origins and may be caused by a mutation in a gene linked to our sleep-wake patterns.

How is SAD treated?

The National Institute for Health and Clinical Excellence (NICE) recommends that SAD should be treated in the same way as other types of depressions. A GP can therefore prescribe antidepressants which work by adjusting chemical imbalances in the brain, or suggest psychological treatments such as cognitive behavioural therapy (CBT) which changes negative patterns of thinking.

SAD is also commonly treated with light therapy (also called phototherapy). This involves sitting in front of a special ‘light box‘ which simulates sunlight. The extra intensity of light is thought to encourage the brain to produce less melatonin and more serotonin to reduce sleepiness and boost mood.

The NHS does not provide light therapy and says its effectiveness is uncertain but the Royal College of Psychiatrists recommends 30 minutes to one hour of light therapy daily.

Commercial lightboxes vary in price depending on the light intensity delivered but 2500 lux is the minimum needed to work.

Alternative Remedies & Self-help

SAD sufferers are advised to get outside in natural daylight and to keep active.


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