Background: Bright light therapy improves the symptoms of seasonal affective disorder by activating the suprachiasmatic nucleus, which helps regulate the circadian rhythm. Because bright light therapy also activates depression-associated neurotransmitter systems (e.g., the serotonin, norepinephrine, and dopamine pathways), it could also improve the symptoms of major depressive disorder. This may be particularly useful in older persons, who have less overall suprachiasmatic nucleus stimulation because of age-related declines in photoreceptor activity and who tend to be exposed less often to bright environmental light. Lieverse and colleagues conducted a double-blind, randomized, placebo-controlled trial to determine the effectiveness of bright light therapy in older persons who have major depressive disorder.
The Study: Investigators randomized a total of 89 patients who were 60 years and older with major depressive disorder to receive light therapy via one of two types of light boxes. Participants received bright pale blue light treatment (7,500 lux) or a biologically inactive dim red light treatment (50 lux) for one hour each morning for three weeks. Depression severity was measured with the Hamilton Rating Scale for Depression (HAM-D) just before the start of treatment, at the end of the three-week intervention, and again three weeks after treatment concluded.
Results: At the end of the three-week intervention, no difference was noted between groups in the number of persons responding to therapy (20 in the bright light therapy group versus 18 in the placebo group; P = .20). However, mean HAM-D scores improved more in the bright light therapy group than in the placebo group (43 versus 36 percent reduction in depression severity, respectively; P = .03). Three weeks after the intervention ended, the difference in HAM-D score improvement was even more pronounced (54 versus 33 percent reduction, respectively; P = .001), and significantly more patients receiving bright light therapy had responded to treatment compared with those receiving placebo (23 versus 15, respectively; P = .05; number needed to treat = 5). No effect was noted when possible confounders were studied (e.g., antidepressant use, atypical depressive features, seasonality of symptoms, treatment resistance). No differences in adverse effects were noted between groups. No hospitalizations or suicides occurred in either group.
Conclusion: In older patients with nonseasonal major depressive disorder, bright light therapy improved depressive symptoms better than placebo after three weeks of treatment. The proportion of responders in the treatment group increased three weeks after completion of therapy, and depressive symptoms were further reduced during this time. These effect sizes are comparable to effects reported for antidepressant therapy. These findings support the use of bright light therapy for persons who decline or are unable to tolerate antidepressant therapy. Further studies are required to determine the prolonged effects, and effects of long-term use, of bright light therapy in this population.