Feeling Depressed? Look on the Bright Side
It was late June in Manhattan, and with the sun beating down on the tarred roads and paved sidewalks, the last thing you would imagine would be on anybody’s mind was light therapy – the process of exposing one’s self to bright light in order to feel better. Yet, there I was attending the latest meeting of the Society for Light Treatment and Biological Rhythms (SLTBR). To my surprise, there was little mention of seasonal affective disorder (SAD), for which it is now an established first-line treatment. Rather, much of the emphasis was on bright light as a remedy for low mood and energy at any time of the year.
In a way, this should have not have been news. In fact, a 2005 meta-analysis by Golden and colleagues, published in the American Journal of Psychiatry, had already concluded that exposure to bright light is effective for non-seasonal depression; a more recent meta-analysis by Al-Karawi and colleagues confirms these earlier conclusions, as do some impressive individual studies. For example, an 8-week study of 122 depressed outpatients by Lam and colleagues at the University of British Columbia, published earlier this year, found that bright light therapy was significantly superior to a placebo treatment and at least as good as fluoxetine (the generic form of Prozac). In addition, a combination of light therapy plus fluoxetine produced the most consistent results. Controlled studies have also shown that bright light therapy is effective for depression in specific subgroups, such as elderly people.
At the SLTBR, Sit from the University of Pittsburgh and colleagues presented data showing that bright white light therapy administered at midday was significantly superior to a dim red light control in 46 people with bipolar depression. Their findings are consistent with a meta-analysis of light therapy for bipolar depression by Tseng and colleagues in Taiwan. Their findings are especially significant because depression is a major problem for people with bipolar disorder despite excellent medical care.
[Video 2:09] Seasonal Affective Disorder, My Personal Story
It now appears that light therapy may benefit people with flagging mood and energy following physical ailments. In an encouraging study presented at the SLTBR, Redd of Mount Sinai University and colleagues randomly assigned 54 cancer survivors to either bright white light treatment or a dim red light control. They found a significantly superior antidepressant effect in those receiving bright light. In addition, analysis of wrist activity data in the two groups showed strengthened circadian rhythms in the bright light group after treatment. Their findings suggest that light therapy may exert at least some of its benefits via its effects on the body’s clock.
Circadian (approximately 24-hour) rhythms in many physical functions are found in all animals and are orchestrated by a small body of neurons called the suprachiasmatic nucleus (SCN) of the hypothalamus, so named because it is located directly above the point at which the optic nerves cross (the optic chiasm). Environmental light entering through the eyes exerts a powerful effect on the SCN and thereby on circadian rhythms, influencing their strength and timing. Thus, bright (as opposed to dim) light may improve mood and energy by strengthening circadian rhythms. Genetic studies have uncovered specific genes that regulate the biological clock – genes that are identical in mice and men. In one intriguing SLTBR presentation, Albrecht from the University of Fribourg, Switzerland presented data showing that mice with abnormal clock genes (as a result of either mutations or experimental disruption) exhibited impaired behavior in animal models of depression. Both the human and animal data presented at the meeting suggest that abnormal biological clock functioning might caused depression, and that bright light therapy may improve depression-type symptoms by strengthening the body’s clock.
The situation is probably more complicated though, and there are other persuasive theories as to how bright light acts as an antidepressant – for example deficient brain serotonin transmission. Antidepressants such as Prozac are believed to work by boosting brain serotonin functioning. Some studies suggest that light therapy may act in a similar way. In the most compelling of these, Lambert and colleagues in Melbourne, Australia took blood samples from the internal jugular veins of 101 healthy men and found that the rate of production of serotonin in the brain was directly related to the duration of bright sunlight on that day.
In my clinical experience (confirmed by colleagues I have polled), light therapy is rarely considered for non-seasonal depression, which is unfortunate. Major depression is a common problem, affecting approximately 1 in 7 people during the course of their lifetime. It can cause serious distress, disability, and even death. A significant percentage of affected people remain depressed despite competent treatment (one in three according to one major study). Given the growing body of research showing that light therapy is a well tolerated and effective treatment for depression either on its own or in conjunction with other treatments, doctors should consider using it more often – and patients should ask for it.
The abstracts from the latest SLTBR meeting can be found in the Archive section of sltbr.org.
Golden, RN, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry. 2005 Apr: 162(4): 656-62.
Lam, RW, et al. Efficacy of Bright Light Treatment, Fluoxetine, and the Combination in Patients with Nonseasonal Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2016 Jan: 73(1): 56-63.