Seasonal Affective Disorder, SAD, winter blues, or seasonal depression, is a medical condition caused by the seasonal change in the amount of available sunlight.
People who suffer from this mood disorder experience normal mental health throughout most of the year, but experience depressive symptoms in the darker winter months.
Some people experience a serious mood change when the seasons change or when they find themselves deprived of natural daylight. Loss of natural light can be the result of long winters, rainy weather, night shift work, airplane travel and subsequent jet lag, or just a lifestyle that dictates too much time indoors.
Symptoms of winter blues, or winter depression, are sluggishness, sleep problems, memory loss, the inability to concentrate and loss of mental acuity.
Sufferers of SAD may find themselves generally feeling lethargic and tired and the subsequent craving sweets and carbohydrates and winter weight gain is a common side affect.
Therapeutic light systems that deliver natural sunshine have been shown to be an effective treatment for these symptoms.
Please see the references below for further information.