Light therapy using specially designed SAD lamps can be used in the management of seasonal affective disorder and winter blues. Exposure to bright light sources at certain times of day can help alleviate some of the symptoms of these seasonal complaints.
Seasonal affective disorder and winter blues
Seasonal affective disorder (SAD) is a type of depression occurring during the shorter days of the winter. It is believed to affect up to 7% of the UK population. Many more people suffer from so-called winter blues, a milder form of the condition characterised by symptoms such as lethargy, increase in appetite and difficulty concentrating.
SAD is believed to be cause by a biochemical imbalance resulting from a lack of stimulation of the brain by sunlight. The hypothalamus is part of the brain controlling mood appetite and sleep. In the winter, individuals with SAD produce more melatonin and less serotonin than usual in response to changing signals from the hypothalamus (NHS Choices website).
Light therapy for SAD
Light therapy can be used to alter the body’s circadian rhythm which is the body’s internal clock. By changing the patterns of melatonin production, exposure to light at certain times of the day can alleviate the symptoms of SAD and winter blues. Although the effectiveness of light therapy is difficult to prove due to the lack of a placebo, a body of scientific evidence exists suggesting light therapy is effective.
Light intensity and timing of therapy
Several research studies suggest high light intensities are required for effective treatment of winter blues. The ideal treatment regime is to expose patients to light of at least 10,000 lux for a period of 30 minutes each morning. Morning exposure has been shown to be more effective than therapy at other times of day as it causes a circadian phase advance (Lewy et al, 1998). Lower light intensities can also be effective, but a longer exposure period is required.
To determine the best time for light therapy, individuals can complete a survey based on the Morningness-Eveningness Questionaire (MEQ) devised by Horne and Östberg in 1976. An online version of this survey can be found on the Center for Environmental Therapeutics website. Individuals with a higher MEQ score are “morning” people and should start their light therapy earlier. Terman and Terman published a table for calculating therapy timings from MEQ scores in their review article. According to their calculations someone with an MEQ score of 68 should start their therapy at 05:30, whereas an individual with a lower MEQ score of 20 does not need to start their therapy until 08:30.
Sources
NHS Choices website
Seasonal Affective Disorder Association website
M Terman, JS Terman “Light Therapy for Seasonal and Non-Seasonal Depression: Efficacy, Protocol, Safety and Side Effects” CNS Spectrums 10:647-663 (2005)
AJ Lewy, VK Bauer, NL Cutler “Morning vs Evening Light Treatment of Patients With Winter Depression” Archives of General Psychiatry 55:890-896 (1988)
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Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
Veronica Mitchell - Veronica studied veterinary medicine at Cambridge University before becoming a secondary school science teacher. She enjoys writing about ...
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