It is generally accepted that the weather can affect peoples moods. You can see it in yourself on a sunny day compared to a rainy or gloomy day. In fact there is actually a science to how weather affects your mood. The amount of sunlight has a direct influence on hormone production which in turn influences Melatonin levels. Depending on how sensitive a person is to Melatonin levels, depends on the intensity their mood is altered. And this is no insignificant disorder. In America alone, nearly 35 million people have problems with this condition. SAD is a serious disorder that can be life threatening and the associated depression can be severe.
The amount and intensity of the sun affects the Pineal Gland. The Pineal Gland is found at the base of the brain. With less light (darkness), the Pineal Gland secretes higher levels of Melatonin. Increases in Melatonin levels have a direct relation to seasonal depression. With less sun the Pineal Gland produces more Melatonin.
Ideally your Pineal gland would start secreting melatonin six hours prior to the middle of your nights sleep. Where this is a normal process for most of us every night, you can imagine how imbalanced your levels of melatonin release rates could be in different seasons.
Typically simply turning on more lights is not enough to alter the increased levels, but it can help. Additional basic techniques including keeping your blinds open, physical activity programs, and spending more time in lighted areas. It is important that people suffering from this disorder seek professional assistance. This assistance may be in the form of light therapies including treatments with significant light intensity levels with a diverse spectrum in the mornings (Bright Light Therapy), melatonin supplements, and automated lighting systems for your indoor living environment.
Decreased desire for physical activity
Desire to sleep for longer periods than normal