What is seasonal affective disorder (SAD)?

Many people feel more cheerful in summer than they do in winter, but for those with the condition seasonal affective disorder the difference can be dramatic.

Seasonal affective disorder (aptly known as ‘SAD’) is a type of depression which, in its most common form, strikes only in the autumn and winter months. Once spring and summer come along, those affected feel perfectly well and normal. There is a less common form in which depression only occurs in the summer months.

Among the symptoms experienced by sufferers are:

  • extreme tiredness and lack of energy;
  • the need for more sleep;
  • difficulty waking up in the morning;
  • increased appetite (particularly with a craving for carbohydrates);
  • weight gain;
  • loss of interest in activities;
  • anxiety; and
  • irritability.

What causes SAD?

SAD is believed to be due to the shorter hours of daylight in the winter months. Although we don't fully understand why shorter days can cause depression, it is thought that the following factors might play a part:

  • a disruption in the body's circadian rhythm (or biological clock);
  • changes in the amount of melatonin produced by the body (melatonin is a hormone that has a role in sleep patterns and mood); and
  • changes in the amount of serotonin produced by the body (serotonin is a brain chemical that affects mood).

How can it be treated?

Research has shown that an effective form of treatment for SAD is bright light therapy (also called phototherapy). This involves exposing patients to a bright light from a specially designed light box. Often as little as 30 minutes a day will produce a marked improvement in mood and general well-being after a few days. It is important that those undergoing bright light therapy keep their eyes open but do not look directly at the light source. The ultra-violet part of light (which causes sunburn and possible skin cancers) can be screened out and the treatment is therefore very safe.

Some sufferers from SAD may also benefit from more conventional treatments for depression such as antidepressant medicines or counselling. Sometimes increased exercise and spending as much time as possible out of doors will help those with a mild attack of SAD.

Last Reviewed: 02/09/2018

myDr


References

1. Cools O, et al. Pharmacotherapy and nutritional supplements for seasonal affective disorders: a systematic review. Expert Opin Pharmacother 2018 Aug;19(11):1221-1233. doi: 10.1080/14656566.2018.1501359. Epub 2018 Jul 26. 2. BMJ Best Practice. Seasonal Affective Disorder. Updated June 2018. https://bestpractice.bmj.com/topics/en-gb/985/pdf/985.pdf