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Visions Journal

A reminder that this article from our magazine Visions was published more than 1 year ago. It is here for reference only. Some information in it may no longer be current. It also represents the point of the view of the author only. See the author box at the bottom of the article for more about the contributor.

Light Therapy

Helping the winter blues and more

Dr. Edwin Tam, MD, FRCP

Reprinted from the "Treatments: What Works?" issue of Visions Journal, 2015 15 (4), pp. 26-28

What in the world is light therapy? Don’t we all get light all the time when we’re awake? Why would anyone need that?

Light therapy is one of the lesser known treatments in mood disorders, but one that has a very important role for a certain type of depression.

What is SAD?

Winter depression, or seasonal affective disorder (SAD), is a type of depression that mostly strikes in the winter (there is a very rare form that shows up only in summer). Patients with SAD get triggered into depression by the onset of fall, and get better in the spring.

What is the trigger? Scientists know that light is very important marker for seasonal patterns in nature. Light is how hibernating animals figure out the seasons are changing. They monitor how long the days are by when it gets dark; shorter days mean winter is coming, and it’s time to hibernate.

Could the brain of a SAD patient be picking up on the changing seasons by measuring the length of days? If so, this brain certainly isn’t being fooled by the indoor lights that make all our days longer.

And, could it be that very bright light closer to outdoor light would help in this situation?

Light therapy: How might it help SAD?

There isn’t one theory that fully explains the effects of light therapy on everyone, and it may work differently for different people. But it has been shown to work well for SAD, or winter depression—65% of people with SAD get a good response over four to eight weeks.1

Light therapy began, in 1984, with bright light from a light box with fluorescent tubes. The light box was used daily, for several hours in the morning and in the evening, to try to make the day seem like a summer day. It was used by patients with SAD... and their depression got better.2

How does light help depression? One theory is that depression in SAD patients is like hibernation in animals. Hibernating animals eat more, then sleep more as their body systems slow down. Depression involves low energy, and often in the case of SAD, eating and sleeping excessively. By switching SAD patients back into summer mode, light therapy may be snapping them out of this hibernation equivalent.

Another theory is that depression in SAD patients is like jet lag. When they get up on winter mornings, the darkness makes them think it’s earlier than it actually is. Their body clocks become out of synch with the external clock time, and they end up feeling “jet-lagged,” with tiredness, poor concentration and poor mood. Since bright light is a known factor in setting the body clock, light therapy in the morning would help synch up the clocks.

In addition, there is evidence that light therapy works by increasing brain levels of neurotransmitters such as serotonin, noradrenaline and dopamine, which may be low in patients with depression.3

It’s possible that it might work for non-seasonal depression. While this needs to be explored further, a collaborative Canadian study involving the University of British Columbia has just been completed (not yet published) showing that light therapy, either alone or combined with fluoxetine (Prozac), was effective and well tolerated by patients with non-seasonal depression.

Another use has been to help people adjust to shift work. Some small studies have also shown it helps with eating disorders (bulimia). This is not surprising as increased eating is often seen in SAD, and a seasonal pattern is noted in up to 40% of people with bulimia.4

About the author

Edwin is Clinical Associate Professor at the Department of Psychiatry, University of British Columbia, and UBC Hospital. He works with seasonal affective disorders in the UBC Hospital Mood Disorders Outpatient Clinic

  1. Westrin, A. & Lam, R.W. (2007). Seasonal affective disorder: A clinical update. Annals of Clinical Psychiatry, 19(4), 239-246.

  2. Rosenthal, N.E., Sack, D.A., Gillin, J.C. et al. (1984). Seasonal affective disorder: A description of the syndrome and preliminary findings with light therapy. Archives of General Psychiatry, 41(1), 72-80.

  3. Sohn, C.H. & Lam, R.W. (2005). Update on the biology of seasonal affective disorder, CNS Spectrums, 10(8), 635-646.

  4. Lam, R.W., Goldner, E.M., Solyom, L. et al. (1994). A controlled study of light therapy for bulimia nervosa. American Journal of Psychiatry, 151(5), 744-750.

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