Some people find that symptoms of SAD can adversely affect daily living. For these patients, light therapy — or phototherapy — can be an effective method of treating seasonal depression.

Seasonal affective disorder (SAD) is considered a subtype of depression. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (2000), a SAD diagnosis must meet the following criteria:

  • Depressive mood and behavior with no other explanations
  • Experience of depression and other symptoms for at least two consecutive years, during the same season
  • Periods of depression followed by periods without depression.

The Biochemical Evidence

The main cause of winter-onset SAD seems to be the reduction in sunlight associated with shorter winter days. Reduced sunlight appears to disrupt your body’s internal clock, interfering with natural body rhythms that regulate everything from appetite to sleep cycles.

Reduced sunlight exposure can cause a drop in serotonin, a brain chemical that regulates mood, perhaps leading to seasonal affective disorder. According to the American Psychiatric Association (2010), seasonal change may also disrupt the balance of melatonin, a hormone associated with sleep patterns and mood.

Ultimately, treating seasonal depression should restore the body’s natural chemical balance. SAD patients may benefit from light therapy, which appears to have none of the adverse side effects of more invasive medication.

Light Therapy and SAD

When treating seasonal depression with light therapy, the patient sits in front of a light box or wears a light visor for 30 to 90 minutes a day. An article published in the American Family Physician (2006) reports that light therapy is most effective early in the day.

SAD treatments sometimes integrate a “dawn simulator,” a light activated by a timer. A dawn simulator mimics a natural sunrise by turning on early in the morning and gradually increasing in brightness. This allows you to wake up naturally, without the use of an alarm clock.

When used properly, light therapy appears to have very few side effects. However, then these effects do occur, they may include:

Light therapy too late in the day can result in insomnia. People with manic depressive disorders, skin that is sensitive to sunlight or medical conditions that make their eyes vulnerable to sunlight damage should be particularly careful with light therapy.

Since tanning beds produce high levels of ultraviolet (UV) rays that harm both your eyes and your skin, these lights aren’t recommended for light therapy and SAD.

A Word of Caution

Light therapy is sometimes called “blue light therapy.” Although many people are under the impression that blue light therapy is more effective than white light, recent studies published in Science Translational Medicine (2010) and Neuron (2010) suggest that blue light therapy offers no benefits over regular white light. Blue light therapy lamps may even increase the risk of macular degeneration or blindness.

Consult with your healthcare provider before using light therapy, particularly blue light therapy, for treating seasonal disorder.


American Psychiatric Association. (2010). Seasonal affective disorder. Retrieved July 10, 2010, from

American Psychiatric Association. (2000). Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Washington, DC: American Psychiatric Association.

Family Doctor. (2010). Retrieved July 14, 2010, from

Gooley, J. J., Rajaratnam, S. M. W., Brainard, G. C., Kronauer, R. E., Czeisler, C. A.

 Posted on : June 14, 2014