Introduced in the 1980s, bright light therapy has become a mainstay of treatment for Seasonal Affective Disorder (SAD), a subtype of depression with symptoms that manifest in winter and remit in summer. An increasing number of studies have also reported light therapy to be effective in the treatment of nonseasonal depression and its subtypes, including postnatal depression, bipolar depression, premenstrual depression, and treatment-resistant depression.1 Light therapy may have certain advantages over pharmacologic treatments for depression, such as a rapid onset of antidepressant effects, mild and infrequent adverse effects, and cost-effectiveness.
Patients undergoing light therapy situate themselves near a light box fitted with fluorescent tubes and a diffusing screen to filter out ultraviolet light. Sessions typically take place in the morning for a prescribed duration of time. The eyes must be kept open, but looking directly at the light source is neither required nor recommended.2
The mechanisms by which light therapy exerts its antidepressant effects have yet to be fully clarified. One leading hypothesis is that light therapy corrects phased-delayed circadian rhythms by activating the suprachiasmatic nucleus, the body’s master clock, through an ocular receptor mechanism.3,4
Abnormal circadian rhythms and sleep cycles are common across mood disorders, not just SAD. The relevance of circadian rhythms to nonseasonal depression is evinced by a high frequency of sleep complaints in affected patients, as well as the predictable daily pattern of symptoms that many patients experience, frequently involving a greater severity of symptoms in the morning.5 The most recent available Cochrane review on the topic of light therapy for nonseasonal depression, published in 2004, concluded that it offers “modest though promising antidepressive efficacy, especially when administered during the first week of treatment, in the morning, and as an adjunctive treatment to sleep deprivation responders.”6 However, there are few studies evaluating bright light therapy. Methodologically valid clinical trials in light therapy have proven challenging because it is difficult to provide a placebo equivalent. Patients who are aware that light therapy is the modality being investigated may have higher expectations for bright light as opposed to the dim red light typically used as a control.7,8
According to evidence from a recent meta-analysis, light therapy appears to be safe and efficacious in older patients with nonseasonal depression. 8 Research suggests that impairments in the amplitude and timing of circadian rhythms may increase with aging.9 Perhaps relatedly, the risk of depression is also known to be higher in the geriatric population. While estimates vary, most studies indicate that the prevalence of depression in older adults exceeds 10%, which is more than double the rate of 4.4% estimated for the general global population.10,11 Nursing home residents are especially prone to depression, with a rate 3- to 4-four times higher than that in community-dwelling elderly.12 The elderly population may be particularly in need of expanded therapeutic options for depression due to concerns that benefit/safety ratio for antidepressants may be unfavorable in this age group.13 Moreover, antidepressant treatment failure and medication nonadherence are more common in older patients with depression compared with younger age groups.14
For their meta-analysis of studies examining light therapy for nonseasonal depression in older adults, Xue Zhao, MD, of Nanjing University of Science & Technology, Nanjing, China, and colleagues analyzed published research on nonseasonal depression involving participants older than 60 years and diagnosed with depression using the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, or standardized depression scales. Analysis of the 6 studies that ultimately met the researchers’ criteria for inclusion demonstrated a statistically significant difference between light therapy and control groups in improving depressive symptoms in older patients (z =2.88, P <.001). While light treatment time, light types, and light intensity were shown to be potentially influential factors of light therapy for geriatric nonseasonal depression, no statistically significant differences were observed for these variables. According to the authors, that lack of statistical significance was due to limited sample size. No differences in side effects for light treatment vs placebo were reported.8
Amanda Leggett, PhD, a research professor at the University of Michigan, recently led a pilot study on bright light for the prevention of late-life depression.14 She explained to Psychiatry Advisor that certain barriers could limit the widespread use of light therapy in the geriatric population. “Some older adults prefer to manage their mood on their own,” she noted. “I’ve had individuals ask, “why can’t I just open the blinds and get light that way”? Since it is a device, it may take some work to make sure older adults are comfortable with it and understand its potential usefulness. Further, while it appears light therapy is safe for the eyes, some research studies exclude participants with eye disorders such as macular degeneration, glaucoma, and cataracts, all of which are prevalent among older adults. This may limit our understanding of whether light therapy is safe and/or effective for older adults with these conditions. The authors of the review do not discuss exclusion criteria, so the generalizability of these studies is unclear.”
Dr Leggett noted that more research on light therapy for late-life depression is warranted. “I think future research should consider whether there are certain subgroups of individuals with depression who would benefit most from light therapy. For example, given circadian disruption, perhaps this therapy might be most beneficial for individuals with depression who also report sleep disturbance.”
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4. Byrne J. Ocular mechanism key to light therapy for seasonal affective disorder. Primary Care Optometry News. https://www.healio.com/optometry/primary-care-optometry/news/print/primary-care-optometry-news/%7B83c7e8c7-9657-4611-a174-289b0ea639a3%7D/ocular-mechanism-key-to-light-therapy-for-seasonal-affective-disorder. Published December 2006. Accessed April 19, 2018.
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11. Depression and Other Common Mental Disorders: Global Health Estimates. Geneva: World Health Organization; 2017.
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14. Leggett AN, Conroy DA, Blow FC, Kales HC. Bright light as a preventive intervention for depression in late-life: a pilot study on feasibility, acceptability, and symptom improvement. Am J Geriatr Psychiatry. 2018;26(5):598-602.