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HealthInfo Waitaha Canterbury

Seasonal affective disorder (SAD)

Mate pāngā ā-kaupeka

Seasonal affective disorder (known as SAD) is a condition where people develop symptoms of depression every year, during the darker winter months.

People usually only get SAD in countries that have a winter with darker and shorter days, like New Zealand. A less severe condition called the winter blues is also very common. Women are more likely to be affected by SAD or the winter blues.

Health professionals do not know the exact cause of SAD. But they think it's caused by reduced sunlight levels. Sunlight affects the number of nerve messages that you send from your eyes to parts of your brain. The activity of nerve messages caused by sunlight affects the level of certain brain chemicals (such as serotonin) and hormones (such as melatonin). These chemicals and hormones are thought to affect your mood. So, with less sunlight in the winter months, changes in the balance of these chemicals and hormones may affect your mood and trigger depression.

Diagnosing SAD

The symptoms of SAD are very similar to non-seasonal depression. If your symptoms occur all year round, it's likely that you have depression. But some symptoms are more common in SAD and less typical in non-seasonal depression. These symptoms include: a craving for sweet things, putting on weight, increased sleepiness, sleeping a lot and feeling like your arms and legs are heavy.

Treating SAD

You may be able to help yourself with SAD.

If you need more help talk to your general practice team. They can advise on other treatments that include antidepressant medication, talking therapies and for some people, light therapy using a special light box.

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Written by HealthInfo clinical advisers. Last reviewed May 2023.


Page reference: 52079

Review key: HISAD-52079