Light Therapy for Seasonal Affective Disorder (SAD)

What is Seasonal Affective Disorder (SAD) / Winter Depression

Seasonal Affective Disorder, (SAD) or Winter Depression, is defined as a Major Depressive Disorder with a seasonal pattern. Light therapy is usually recommended as a first line intervention for this condition because experience, and most clinical studies, have found that it is more effective than antidepressant medications. Light therapy also does not have the pharmacological side effects associated with mood influencing drugs, and generally involves less than 1/2 hour of daily exposure to a light therapy lamp. It is a natural intervention that has the same effect on a person as traveling towards the equator, where the days are longer.

SAD is a form of depression that occurs in individuals whose moods are sensitive to seasonal changes. For these people, the shorter days in winter causes "winter blues" that interferes with their ability to function normally. Seasonal Affective Disorder is linked to the functioning of the internal body clock, a small structure in the brain of all mammals, including humans that influences seasonal changes in eating, sleeping, and social activity.

In winter the body clock of mammals senses the shortening day length and responds by promoting sleep in the mornings and increased appetite in the evenings, and a reduction in aggression and breeding behaviors. These behavioral changes encourages mammals to conserve their energy and gain weight to survive harsh winter conditions. Humans often experience these changes as a reduction in energy levels and a tendency to gain weight in the winter months. More on The effect of the seasons on human physiology..

How Light Therapy relieves SAD

The basis of light therapy is to lengthen perceived day length, restoring the body clock to a summer mode. While most people respond to the shorter day of fall and winter with behavioural changes related to sleep and energy levels, for some people the changes in the functioning of the body clock that occur in winter results in depressed mood. Milder forms of these lowered mood states are known as the Winter Blues, while more serious cases result in depression. (SAD)

Although seasonal depression can affect mood in the same manner as Major Depression, SAD is usually an atypical depression. People suffering from Major Depression often have trouble sleeping or eating, while people with SAD will often have trouble waking in the morning, and often have increased appetites, particularly in the evening. The increased appetite in the evening, particularly for foods with high starch or sugar content, is called Carbohydrate Cravings..

Properly timed light therapy influences some neural pathways in the brain that use serotonin as a primary neurotransmitter. It appears that serotonergic activity in the brain is affected by the influence of light on the activity of the body clock. This can explain the clinical studies finding light therapy to be an effective treatment for non-seasonal Major Depression, as well as for Bipolar Depression.

SAD was originally thought to be a variant of Bipolar Depression, and some people with Bipolar Disorder find their depressive episodes are deeper and more frequent in the winter months. Light Therapy, recognized as the first line treatment SAD / Winter Depression, has also been shown to be effective for treatment of both non-seasonal Bipolar Depression and Major Depression in clinical studies.
More on Therapy for Non-Seasonal Depression.
Clinical Studies with Lo-LIGHT lamps for Major Depression and Bipolar Depression.

It was originally believed that exposure to bright light is needed to influence brain physiology and reset the body clock. However, independent studies in laboratories around the world have found that Sunnex Biotechnologies low-intensity Lo-LIGHT lamps influence the body clock as effectively as bright light lamps, but in a safer and more comfortable manner. MORE

Lo-LIGHT therapy lamps do not use high intensity light, The GreenLIGHT technology is a selected narrow spectrum of visible green light wavelengths to which the body clock is particularly sensitive. The hazard that exposure to blue light wavelengths from bright light and blue light therapy lamps is becoming more widely recognized, and concerns about the contribution to age related blindness from exposure to blue light has now been expressed by several retinal specialists. The combination of low intensity and the elimination of blue light makes Lo-LIGHT lamps less hazardous than normal indoor lighting, and can be used without risk of eye damage even by people with pre-existing ocular damage. Lo-LIGHT therapy lamps have been used for over 15 years to safely and comfortably help customers feel happier and more energetic through the winter months.

More information on how The Body Clock affects mood
Click for reference material concerning light therapy for Winter Depression and Seasonal Affective Disorder



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