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Causes of Seasonal affective disorder

The cause of SAD is not fully understood, but is thought to be linked to reduced exposure to light during the winter months.

Researchers have shown that bright light makes a difference to brain chemistry, but it is not clear exactly what the effect is. One theory is that light stimulates a part of the brain called the hypothalamus, which controls mood, appetite, and sleep. In people with SAD, lack of light and a problem with certain brain chemicals prevents the hypothalamus from working properly.

Melatonin, a sleep-related hormone released in the brain, has also been linked to SAD. This hormone is thought to cause symptoms of depression and is produced at increased levels in the dark.

SAD may also have a genetic cause. It has been shown that you are more likely to develop SAD if you have a close relative who has it.

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