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Light Therapy for Treating Seasonal Affective Disorder

Madeline Davis

October 5, 2009


        By the time fall comes around, some people love to see the leaves falling from the trees and feel the temperature get colder. However, another group of people knows that with the changing season comes a loss of energy, chronic fatigue, and depression. When a person gets depressed as the seasons change, they are known as having Seasonal Affective Disorder. Seasonal Affective Disorder mainly occurs in the fall or early winter but can occasionally occur in the spring or summer as the weather becomes warm. Seasonal Affective Disorder will occur at the same time every year for a certain individual and can greatly affect their way of life for many months. Despite the effects of Seasonal Affective Disorder, light therapy has been seen as an effective way of treating the symptoms of Seasonal Affective Disorder.

What is Seasonal Affective Disorder?     

Text Box:  The prevalence of Seasonal Affective Disorder varies by geographical region. In northern New England, it appears in about 10% of the general population. In the Washington D.C./Baltimore area, it appears in about 5% of the population. In southern California or Florida, it appears in less than 2% of the population ( Causes of Seasonal Affective Disorder include a person’s biological clock and their melatonin and serotonin levels. In the fall when the amount of light during the day changes, this change of light affects a person’s biological clock, or circadian rhythm, on when they should sleep and when they should wake. This change in the circadian rhythm can lead to a person feeling depressed. The change in the season can also affect the levels of the hormone melatonin. Melatonin affects a person’s sleep patterns and moods, which therefore can lead to seasonal depression. Serotonin is a neurotransmitter in the brain that also plays a role in a person’s mood, and a drop in serotonin can lead to depression (




Text Box:  A common treatment for Seasonal Affective Disorder is by using light therapy, sometimes known as phototherapy. The idea of light therapy is that a person with Seasonal Affective Disorder is exposed to an artificial light that mimics natural, outdoor light. The exposure to this bright light is claimed to change a person’s circadian rhythm and suppress melatonin levels, therefore preventing depression. Light travels through the retina to the hypothalamus in the brain, which is involved in regulating the body’s natural clock and is why light or lack of light can alter the body’s circadian rhythm. The duration of the light therapy session, the strength of the light, and time of day is dependant upon an individual’s need. The length of the light therapy session is correlated with the strength of the light. For example, a person may use a 1-hour session with 5,000 lux once a day or a ½ hour session with 10,000 lux. Lux is a measurement of light intensity that corrects itself for sensitivity on the eye (Lam and Westrin, 2007). In comparison, a bright sunny day can have a light strength of 10,000 lux. The time of day in which a person will engage in a light therapy session also depends on the individual as well. There are two major types of Seasonal Affective Disorder. The first type is “Phase Delayed.” This means patients have trouble waking up in the morning and feel sluggish for a long time after. They may become sleepy again in the afternoon or early evening. The best time of day for light therapy is in the morning between 6 and 8 a.m. This affects about 80% of Seasonal Affective Disorder patients. The second type is “Phase Advanced.” These patients feel most awake and least depressed in the morning but their energy levels gradually decrease after noon. The best time for treatment for these patients is from 3-7 p.m. This affects about 20% of Seasonal Affective Disorder patients (


Claims about Light Therapy  

The information about light therapy above comes from two major sources on the internet. The first is the Mayo Clinic website. The Mayo Clinic is generally a very reliable source for health information. It is a general medical practice that is a source of information for almost any health treatment. The Mayo Clinic has four hospital locations around the country. The second website is the Light Therapy Products website. This website was proved credible as the Mayo Clinic website supported the information discussed on this website. These two websites alone provided sufficient information on light therapy and other websites, though in favor of the effectiveness of light therapy, were not necessarily credible. Along with these two websites on general information about light therapy, many studies have been completed that have proven the effectiveness of light therapy.



An article by Robert H Howland titled “Somatic Therapies for Seasonal Affective Disorder” published in the Journal of Psychosocial Nursing & Mental Health Services reviewed many studies done to test the effectiveness of various treatments on Seasonal Affective Disorder, including light therapy. One study done by Terman et al. in 1989 reviewed twenty-five studies. These studies revealed that one week of morning treatment produced higher success rates of eliminating Seasonal Affective Disorder compared to evening and midday sessions. Morning treatments produced a 53% rate while evening sessions produced 38% success and midday treatments only produced 32% success. In a more recent study done by Golden et al. in 2005, dawn simulation was tested as an effective measure in treating Seasonal Affective Disorder. The studies used light starting before dawn from 0 lux to 200 to 300 lux in one to 2.5 hours. The placebo group had a light increase to less than 5 lux in less than fifteen minuets. This treatment done in the study proved effective at treating Seasonal Affective Disorder. As the sun was rising in the morning, it provided brighter light to alter the body’s biological rhythm. This journal article concluded that the most effective way of treating Seasonal Affective Disorder is by exposing bright light to patients shortly after awakening in the morning (Howland, 2009).


“Seasonal Affective Disorder: A Clinical Update” was written by Asa Westrin and Raymond W. Lam and published in Annals of Clinical Psychology. This article reevaluated many studies done to test the effectiveness of various means of treatment, including light therapy. One problem in this evaluation was that many studies done did not follow strict methodologies. Of these studies, eight studies passed stricter guidelines and were analyzed in this article. In these studies, improvement for the patients was seen after only one or two weeks. However, to show clear responses to light therapy, some patients will need two or three weeks. After light therapy is discontinued, patients will relapse back into depression. A recent study referenced in this article compared the effectiveness of light therapy to antidepressant medication. This was a double-blind treatment where patients were either given 10,000 lux of light therapy and a placebo pill or 100 lux light therapy and 20 mg/day of fluoxetine. Both groups of participants improved in eight weeks. Both groups lowered depression scores, clinical response rates were 67% successful for both groups, and remission rates were 50% for light therapy and 54% for fluoxetine (Lam and Westrin, 2007).


Light room therapy effective in mild forms of seasonal affective disorder--a randomised controlled study” written by C. Rastad, J. Ulfberg, and P. Lindberg and published in Journal of Affective Disorders studied the effectiveness of light therapy rooms on the treatment of Seasonal Affective Disorder. This study took place in Sweden with fifty-one participants randomized to participate in either light room therapy or a control situation. Participants were present in these light therapy rooms for 1.5-2 hours each day from 6:00-9:00 a.m. in four different clinics from October to February. Participants did not have to travel more than thirty kilometers to these clinics. This study was conducted for two consecutive winters, in 2002-2003 and 2003-2004. The result of this study was that after ten days, winter depression was reduced by light room therapy according to self-report. After a three-week waiting period and then the one-month follow-up, these patients still reported reduced depression (Lindberg, Rastad, & Ulfberg, 2008).



After reviewing these clinical studies on the effectiveness of light therapy on Seasonal Affective Disorder, it can be concluded that the original websites were correct in their claims that light therapy does successfully reduce a person’s depression in the fall and winter months. Within these articles discussed, many studies were reviewed and the general consensus was that light therapy does reduce or eliminate depression brought on by Seasonal Affective Disorder. If a person suffers from seasonal depression, nothing should be a barrier to receiving treatment. Light therapy does not require much intervention by health professionals and can easily be performed at home with portable light therapy boxes. With such an easy and successful treatment, no person should ever dread the winters again.



About Mayo Clinic. (n.d.). Retrieved October 4, 2009, from

Howland, R. H. (2009). Somatic Therapies for Seasonal Affective Disorder. Journal of Psychosocial Nursing & mental Health Services, 47(1), 17-20.

Mayo Clinic Staff. (2008, October 7). Light therapy. Retrieved October 3, 2009, from

Mayo Clinic Staff. (2009, September 24). Seasonal affective disorder (SAD): Causes. Retrieved October 3, 2009, from

Rastad, C., Ulfberg, J., & Lindberg, P. (2008). Light room therapy effective in mild forms of seasonal affective disorder--a randomised controlled study. Journal of Affective Disorders, 108(3), 291-296.

SAD Seasonal Affective Disorder. (n.d.). Retrieved October 3, 2009, from

Westrin, A., & Lam, R. W. (2007). Seasonal Affective Disorder: A Clinical Update. Annals of Clinical Psychiatry, 19(4), 239-246.




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