Use a SAD Light to Combat the Winter Blues

Two weeks ago most of the country turned their clocks back and it got noticeably darker in the late afternoon. As fall slips into winter across Canada, daylight hours decline significantly.  In Winnipeg for instance, daylight hours dwindle from about 13 hours in September to just over 8 hours in December. Limited sunlight exposure is a major factor in “Seasonal Affective Disorder” (SAD).

Seasonal Affective Disorder is a syndrome that reoccurs annually in the late fall and winter. Various studies have estimated it’s prevalence between 1.7% and 2.2% of the population. It affects more women than men, and it increases with age until the mid 50’s and declines in older individuals1.

Common symptoms include: sadness, anxiety, irritability, premenstrual difficulties, decreased energy, activity, and libido. Many people also feel sleepy during the day and experience increased appetite, particularly for carbs².

Although not fully understood, what is known is that SAD is complicated and varies by individual, but no single factor appears to cause the syndrome entirely.  However, disruption of our normal 24 hour circadian rhythm, melatonin secretion, seasonal changes in serotonin metabolism, and genetics, all play contributing roles. 

“Light Therapy” is normally the first-line of treatment for Seasonal Affective Disorder and is 60% to 90% effective.  There have been over 60 studies evaluating light therapy.  It is generally accepted that a minimum of 2500 lux is necessary for effective treatment.  For reference, midday sunlight is 50,000 lux, outdoors on a cloudy day ranges from 1000 to 5000 lux, and bright office lighting is from 300 to 500 lux2.

The “dose” can vary, but the normal starting point is 10,000 lux for 30 minutes per day.  Alternatively, 1-2 hours at lower intensity 2500 lux.  Light therapy should stat early in the morning, just after awakening.  Most people respond within one week2.

Common side effects include: headache, eye strain, nausea and agitation.  Normally symptoms are mild and can be addressed with lower intensity.  Users should avoid looking directly at the light, there is no therapeutic benefit2.

Overall, using a SAD light is safe and effective for treating Seasonal Effective Disorder.  Various sizes of lights are available and consumers can find these products on-line or at most pharmacies. People should choose lights that have adjustable intensities, in case they experience negative symptoms.  Given the demand for other Covid-19 related medical products like pulse oximeters, fever thermometers and blood pressure monitors, people who feel they are affected by Seasonal Affective Disorder should purchase them now, before the shelves are empty.  This has been the experience on many other medical products related to Covid-19.

For more information on our SAD light products please visit our website;

Author: Mark Beaton, Senor Vice President of Marketing, BIOS Medical


  1. Light Therapy for Seasonal Affective Disorder, A Review of Efficacy, Terman, J. Terman, F. Quitking, P. McGrath, J. Stewart, B. Rafferty.
    1989 American Colleg of Neopsychoparmacology; 2:1-22, 1989
  1. Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder, edited by Raymond W. Lam, Anthony Levitt
    1999 Clinical & Academic Publishing

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