What is Seasonal Affective Disorder (SAD)?
It's common to be affected by changing seasons and weather. Many of us may feel ‘down’ or have the ‘winter blues’ when the days get shorter and colder in the autumn and winter. For example, we might notice that our mood or energy levels drop, or that we’re sleeping or eating a little more.
But if you’ve come to dread the changes in the seasons because these feelings are seriously disturbing your mood and behaviour and are interfering with your everyday life, you may be experiencing a type of depression that doctors call seasonal affective disorder (SAD).
In the majority of SAD cases, symptoms appear during late autumn or early winter and go away during the sunnier days of spring and summer. However, for some people they may begin in spring or summer. In either case, symptoms may start out mild and become more severe as the season progresses. Winter-onset SAD is more common in people living far from the equator where there are fewer daylight hours in the winter. It affects about 5% of the US and European populations, with younger people and women at greater risk.
Symptoms
The symptoms of SAD occur only at a particular time of year. As well as depressive symptoms such as persistent low mood, a loss of interest in daily activities, and feelings of anxiety, despair, and isolation, symptoms specific to winter-onset SAD may include oversleeping, a craving for foods high in carbohydrates, weight gain, and lethargy. Whereas symptoms specific to summer-onset SAD may include insomnia, poor appetite, and weight loss.
Cause
The exact cause of SAD is unknown. Studies have suggested that both forms of SAD are caused by the effect that sunlight has on our body. That’s because our bodies use sunlight to trigger various important functions such as when we wake up. A popular theory is that lower or higher light levels during the winter and summer seasons may affect a part of the brain called the hypothalamus. The hypothalamus is responsible for producing melatonin, a hormone important for maintaining the normal sleep-wake cycle, and serotonin, a hormone that affects our mood, appetite, and sleep. Vitamin D deficiency may also worsen the condition in people with winter-pattern SAD. That’s because our bodies produce vitamin D when our skin is exposed to sunlight, so with less daylight in the winter we may have lower vitamin D levels, which in turn can affect serotonin production. It's also possible that some people are more vulnerable to SAD as a result of their genes, as some cases appear to run in families.
Diagnosis
Speak to your doctor if you think you may have SAD. A diagnosis will depend on whether you’ve had symptoms during the same seasons for two or more years in a row, whether your periods of depression are followed by periods without depression, and if there are any other obvious explanations or causes for your mood changes.
Treatment
Treatments are available to help people with SAD. They fall into four main categories that can be used alone or in combination:
• Psychotherapy
• Antidepressant medication
• Vitamin D supplement
• Light therapy
Things you can try yourself:
• Regular physical exercise
• Eating a healthy, balanced diet
Light therapy
Light therapy involves sitting by a special lamp called a light box, usually for around 30 minutes to an hour each morning to simulate the sunlight that's missing during the darker winter months. The lamps come in a variety of designs including desk and wall-mounted fixtures, as well as sunrise alarm clocks. It's thought the light may improve SAD by encouraging the brain to reduce the production of melatonin and increase serotonin. Talk to your health care provider about light box options and recommendations, so you get one that's best suited to your needs.
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