HealthInfo Canterbury
Seasonal affective disorder (SAD)
Seasonal affective disorder (known as SAD) is a condition where people develop symptoms of depression every year, during the darker winter months.
SAD generally only occurs 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.
The exact cause of SAD is unknown. However, it's thought to be caused by reduced sunlight levels. Sunlight affects the number of nerve messages that you send from your eyes to parts of the 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 a 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. However, 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.
- Increase the amount of sunlight you get. For example, open your curtains, put your work desk near a window, and go outside whenever you can. More costly ideas include trimming or cutting down trees that block your sunlight, and installing skylights in your house.
- Get plenty of physical activity, preferably outside, and during daylight hours. Aim for at least 30 minutes of activity most days. Read about ideas for getting more activity into your day.
- Check out other types of self-care for depression.
If you need more help talk to your GP team. They can advise on other treatments which include antidepressant medication, talking therapies and for some people, light therapy using a special light box.
HealthInfo recommends the following pages
- Healthify He Puna Wairoa – Seasonal affective disorder
Detailed information about SAD and ways to manage it.
- Mental Health Foundation of New Zealand – Seasonal Affective Disorder
Information about SAD, including its causes, symptoms and treatment options.
Written by HealthInfo clinical advisers. Last reviewed July 2020.
Review key: HISAD-52079
