Known as SAD, seasonal affective disorder is a category of clinical depression that follows a seasonal pattern. Prevalence is usually highest during the winter months. Symptoms include a depressed mood, a sense of worthlessness, lethargy, irritability, and a desire to sleep more than usual. SAD sufferers are about 10% of all those diagnosed with clinical depression. SAD is three times more common in women than men. Scientists do not know why.
The cause of SAD is not fully understood. However, the best predictor is the relative lack of exposure to sunlight during Autumn and Winter. This leads to a variety of questions and hypotheses.
- The body uses morning light to coordinate the body’s internal clock, the circadian rhythm. This could lead to melatonin, the hormone that makes you sleep, being disrupted.
- Another hormone, serotonin, affects one’s mood, appetite, and sleep. It is believed that a lack of sunlight may lead to reduced serotonin production. Lower serotonin levels have been associated with depression.
Recommended treatments are diverse, reflecting the above uncertainties:
- Lifestyle measures: Maximizing natural sunlight, reducing stress, exercise, diet, e.g. (1)
- Light treatment: A light box is used to stimulate sunlight exposure.
- Talk therapy, e.g., Cognitive Behavior Therapy.
- Anti-depressant medicine.
In Japan, there is something called gogatsubyo, “May Sickness”, with similar symptoms to SAD. (2) Why the incidence rate of patients increases after the early May national holidays is not clear.
Whilst the causes are not understood completely, the condition needs to be treated seriously.
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