Seasonal Affective Disorder Linked to Melatonin
Symptoms of SAD Depression and Its Causes
As the days of autumn descend into the dreary months of winter, two out of every 100 people will suffer from seasonal affective disorder (SAD) causing fluctuations of mood, chronic fatigue, tiredness, weight gain, irritability and anxiety. In the shorter days of winter it is common for many people to feel the need to hibernate, sleep and eat more, often with an unusual craving for carbohydrates.
Though an accentuation of certain moods occur naturally by seasons, for some people the arrival of winter can result in severe mood disorders characterized by deep depressive episodes and chronic physical fatigue and lethargy that subside during the spring and summer months.
Symptoms of Seasonal Affective Disorder
SAD occurs in susceptible individuals during the winter months and is more common in countries of the northern hemisphere where the days of winter are shorter and gloomier. Symptoms for SAD are similar to those for atypical depressive illness such as hypersomnia (increased sleep), increased appetite with carbohydrate cravings and weight gain with profound fatigue.
For most people SAD symptoms begin in late September to October and peak in December, January and February. Younger individuals, particularly women, are at higher risk. Hereditary genetics may also be a factor in some people.
Although an individual may not have full-blown SAD, some of its symptoms may still be experienced. Many people tend to sleep and eat more, have less energy and experience the “winter blues.” For thousands of people who suffer from severe SAD, it is a debilitating disorder that recurs every winter.
SAD symptoms Include:
- Regularly occurring symptoms of depression (excessive eating and sleeping, weight gain, loss of pleasure and interest in life, anxiety) during the fall or winter months.
- Full remission from depression symptoms occur in the spring and summer months.
- Symptoms have occurred in the past two years, with no nonseasonal depression episodes.
- Seasonal episodes substantially outnumber nonseasonal depression episodes.
- A craving for sugary and/or starchy foods.
Higher Levels of Melatonin Disrupt Sleep Rhythms
Although SAD is an established medical diagnosis, exactly what causes it is uncertain. There is evidence that this seasonal depressive illness is related to variations of light that occur throughout the year. Just as sunlight affects seasonal activities of animals, as seasons change and natural light dissipates there is a shift in our biological “internal clocks” or circadian rhythms. The International Journal of Circumpolar Health (2001 Nov;60(4):548-51) showed that abnormalities in the level of melatonin, a hormone that responds to light, is linked to symptoms of SAD.
Melatonin is a sleep-related hormone secreted by the pineal gland in the brain. In normal levels, this hormone controls the natural rhythm that signals the body to fall asleep and wake up at proper times. However, as days get shorter a lack of sunlight affects levels of melatonin and its precursor serotonin, another hormone that affects mood and that melatonin is produced from.
Melatonin is produced at higher levels than normal when you are exposed to less light. Therefore as the days grow shorter and darker, excess melatonin may be produced causing SAD with symptoms of fatigue, lethargy and irritability. Sufferers oversleep without feeling refreshed, crave carbohydrates and feel anxious and irritable.
For more information on SAD visit: What is Seasonal Affective Disorder.
Dark and Short Days May Cause Depression & Anxiety
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Melatonin May Induce the Need for Sleep
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