SAD

SAD (Seasonal Affective Disorder)

What is SAD (Seasonal Affective Disorder)?

SAD stands for seasonal affective disorder, a type of depression that is due to a lack of exposure to light during the winter. It begins in the autumn (usually October or November) and subsides in the spring (usually March or April).

SAD can simply be a nuisance to live with or severe enough to affect your ability to function from day to day. It affects women more than men and occurs most often during people’s twenties through to their forties.

People with SAD will experience some or all of the following symptoms, starting in autumn, intensifying in winter, and subsiding in spring:

What is the difference between SAD and other types of depression?

The main difference between SAD and other types of depression is that SAD occurs only during the winter months.

In many types of depression, people generally eat and sleep less and lose weight. However people with SAD usually eat and sleep more and gain weight when it is cold and dark outside.

SAD, like other types of clinical depression, is not caused by psychological or social factors, although such stresses can aggravate it. Normal sadness does not generally include these physical symptoms and is situational.

'Christmas blues' can be distinguished from SAD because they are generally not accompanied by physical symptoms. Instead they are caused by the typical stresses of the December holiday season and occur only around that time.

What causes SAD?

SAD seems to run in families. Most people with the disorder have at least one close relative who has had bouts of depression (often SAD) at some time.

Lack of exposure to light seems to be the main trigger of SAD symptoms. There are theories on the underlying biochemical process that is affected by the lack of light.

An abnormality in one or more neurotransmitters and/or hormones is the suspected cause of SAD. Neurotransmitters are the chemicals that carry messages between nerve cells. The neurotransmitter serotonin is considered to be a likely cause of SAD because its concentration in the brain varies with the seasons, the smallest amount occurring during the winter.

Other chemicals under investigation include the neurotransmitters norepinephrine and dopamine, as well as the hormone melatonin. The female sex hormones oestrogen and progesterone may also be involved, since women are more vulnerable to SAD than men, especially in the years between puberty and menopause.

If you think you may be suffering from SAD, you should seek medical advice.

Back to top of page