Have you ever noticed how during rainy, gray days, you feel tired and gloomy, but on sunny days you feel very cheerful and energized? Actually, there is a scientific reason for this. According to scientific research, insufficient exposure to sunlight has been liked with low levels of serotonin and melatonin, carbohydrate craving, sleep disturbance, and weight gain.
Some also feel seasonal mood fluctuation, feeling very much depressed only during winter months. The longest day every year is on June 21, when we experience the summer solstice. This is the time when we are happier this time of the year. After June 21 however, the days get progressively shorter until Dec. 21, when it’s winter solstice. No wonder a lot of people get depressed during the holidays.
The medical term for this season-long condition? It’s seasonal affective disorder or SAD.
SAD is believed to a result by a disturbance in the normal circadian rhythm of the body. Light entering through our eyes influences this rhythm. When it is dark, the pineal gland produces a substance called melatonin that is responsible for the drowsiness we feel each day after dusk. Light entering the eyes at dawn shuts off the production of melatonin. During the shorter days of winter, when people may rise before dawn or not leave their offices until after sunset, these normal rhythms may become disrupted, producing the symptoms of SAD.
There is also evidence linking SAD to a reduced amount of the neurotransmitter serotonin. Serotonin is the feel-good substance that is increased by antidepressants called selective serotonin reuptake inhibitors (SSRIs). This decrease in serotonin production may be responsible for many of the symptoms of SAD, such as depression and carbohydrate cravings.
Light therapies (which use a device that give off bright, white light) and some drugs are used to treat this condition.