Antidepressant medications have historically been the first-line treatment for unipolar depression. However, the efficacy of these drugs is often unclear. Many studies have failed to indicate effectiveness of antidepressant medications when compared with placebos. Most antidepressant medications also require several weeks to achieve full therapeutic benefits. This delay can cause difficulties for individuals who need rapid symptom relief.
Bright light therapy represents a promising new treatment for unipolar depression. Although bright light therapy has been used to treat seasonal affective disorder (SAD) for many years, many researchers indicate that bright light therapy may also help individuals with unipolar depression. As this treatment is nonpharmaceutical, it is also a suitable option for those who must avoid antidepressant medications, such as individuals who are in perinatal and geriatric populations.
In an article published in Sleep Medicine, researchers reviewed several studies examining the effectiveness of bright light therapy and various chronotherapies.1 Researchers, through early results, suggest that these treatments offer unique advantages for individuals with depression. The effects were especially pronounced when these treatments were combined with antidepressant medications or other therapies. However, further research is needed to determine appropriate clinical guidelines.
Depressed individuals commonly report sleep disturbances, and research suggests that these symptoms are often linked to negative treatment outcome. A shift in circadian rhythm appears to be associated with more severe depression.2 Some clinicians speculate that treating these symptoms may relieve depression.
Studies performed on this topic often use bright light therapy to adjust an individual’s circadian rhythm and improve their mood. The relationship between light exposure and mood is well-documented: high light exposure is linked to elevated mood and a lower risk for depression.3 As a result, bright light therapy has been used to treat SAD for decades. Today, it is also considered a promising treatment for nonseasonal depression.
However, few studies have analyzed the effectiveness of using bright light therapy for unipolar depression. In their review article, researchers analyze available data analyzing the efficacy of bright light therapy. They examine various combination treatments, including chronotherapies.
The researchers searched PubMed and PsycINFO for English-language studies on relevant topics. Studies were considered eligible for inclusion if they were peer-reviewed and included at least 5 participants. In each of the selected studies, the main participant sample experienced symptoms consistent with unipolar depression. Studies in which the main sample were diagnosed with bipolar disorder were excluded. Studies analyzing SAD were also excluded, along with studies in which the main participant sample had a primary health concern like cancer.1
Studies using bright light therapy measured treatment patterns using lux-hours. Lux-hours were calculated by multiplying the brightness of the light by the number of hours of treatment. A 10,000-lux treatment administered for 30 minutes would be recorded as 5000 lux-hours.1 These measurements were consistent across the various studies, but the timing and duration of bright light therapy often varied. The investigators noted that these factors likely have significant treatment implications.
In their review article, the researchers observed that each study used different criteria to determine treatment response and remission. Since different study researchers used different rating scales and inventories to assess symptom severity and outcome, it is challenging for researchers to draw sweeping conclusions. However, even if results could not always be quantified, clear patterns often emerged.
The investigators located 18 studies, with a total of 600 participants, analyzing the effects of bright light therapy on unipolar nonseasonal depression in the general population. These studies were published between 1985 and 2016. Participants averaged 7278 lux-hours per day, with a mean treatment duration of 18 consecutive days.1 In addition, the investigators located 9 studies that analyzed the use of bright light therapy as an adjunct treatment and that used bright light therapy along with antidepressant medications.
Researchers of studies reviewing bright light therapy as an adjunct treatment were encouraging, according to researchers. One trial used 5000 to 10,000 morning/afternoon lux-hours of “bright fluorescent light.” During and after bright light therapy treatment, participants continued taking antidepressant medications as per previous care. Seventy percent of individuals in this trial experienced an improvement in mood. Further, 8 between-subjects studies were completed, with 7 indicating effectiveness of bright light therapy.4
A similar trial compared 5000 daytime lux-hours with dim light in 40 participants receiving fluoxetine. This trial noted an improved response following bright light therapy.5 Another study of 29 participants also found that 3 weeks of 10,000 morning lux-hours led to as much symptom relief as imipramine. Further, more individuals in bright light therapy group responded to treatment than participants receiving imipramine alone, or a combination of imipramine and bright light therapy.1
Other trials examined different drugs, including sertraline and venlafaxine. Trial investigators indicated that bright light therapy, when combined with antidepressant medications, produced significantly better treatment response than dim light or drugs alone. In a randomized controlled trial of 122 individuals, both bright light therapy alone and bright light therapy with fluoxetine were shown to have a greater effect than placebos.6 The response and remission rates were highest in groups that combined antidepressant medications with bright light therapy.
However, some studies did not support the efficacy of bright light as an adjuvant to antidepressant medications. One study found that bright light therapy alone produced significant benefits when compared with bright light therapy with antidepressant medications. Another found few differences between groups taking antidepressant medications and groups using a combination of treatments. Cunningham and colleagues noted that some of these studies used evening bright light. Clinical evidence thus far suggests that morning bright light therapy may be the most effective method of treatment for unipolar depression.1
Further, within the studies analyzed, typical lux-hours ranged from 5000 to 10,000, with start of therapy not long after the individuals’ typical wake time.1 Yet, it is currently unclear whether this represents the optimal treatment method. Not all the study researchers analyzed administered bright light therapy using consistent timing. Some also discontinued treatment after just a few weeks, which may not be enough time to achieve full results. According to researchers, more research on the ideal treatment protocol for bright light therapy is needed to standardize clinical guidelines.
The review investigators also examined bright light therapy as a standalone option. During the review, this team isolated 9 studies, published between 1985 and 2013, which used bright light therapy as the only treatment for unipolar depression. Although these studies appeared to show benefits from bright light therapy, results were mixed. Researchers of one study found that bright light therapy was largely beneficial, but less so than a combination of bright light therapy and antidepressant medications. Researchers of another study found no benefit from the use of antidepressant medications when combined with bright light therapy, while researchers of a third suggested that bright light therapy alone was more effective than a combination of treatments.1
Medical literature on this topic reveals similarly mixed results. Various study researchers have used bright light therapy and alternate forms of light as a control. Some study researchers used a dim red light as the control, while others opted for a low-density ion generator. Researchers of self-reporting questionnaires from participants suggested that bright light therapy was generally effective in improving depressive symptoms.1 However, researchers of 3 other studies showed no benefit of bright light therapy over the control.
Most studies using bright light as standalone treatment use shorter treatment duration than adjunct therapy studies, according to researchers. Further, treatment and study protocols vary, as do comparison conditions. Before reaching conclusions about the use of bright light therapy as a standalone treatment, researchers indicated further research must be conducted, including studies using standardized methodology and treatment protocol.
In the United States, over 11.19% of patients who are geriatric report symptoms of depression.7 These symptoms can contribute to adverse health outcomes and early death. Medication may be useful for some of these individuals, but many are already taking medications that are contraindicated for antidepressant medications. Frequent changes in pharmaceutical treatment plans can make it difficult for geriatric individuals to remain on a single medication.1
As a nonpharmaceutical treatment, bright light therapy offers an excellent alternative for patients who are older. Similar benefits are indicated for pregnant and postpartum individuals. In these groups, antidepressant medications treatment is often undesirable due to the risk for negative impact on the child.
Researchers analyzed 3 relevant studies, with a total of 159 participants who were geriatric, comparing bright and dim light as a treatment for depression symptoms. The results of all 3 studies were consistent, with bright light therapy significantly lowering depression scores after 5 days of treatment. In addition, more participants responded to treatment or went into remission following bright light therapy when compared with control groups.1
The investigators also located 4 studies in women who were perinatal with symptoms of depression. One examined the effects of bright light therapy in women who were postpartum and 3 reviewed bright light therapy in women who were antepartum. Clinical benefits of bright light therapy were revealed within 3 weeks,1 but varying treatment durations obscured results. More research is needed to determine the ideal treatment length.
In their review, the investigators also explored other chronotherapeutic treatments for unipolar depression, including sleep deprivation therapy (SDT). SDT involves depriving individuals of sleep time. The amount of sleep restricted can vary. Clinical data have established that approximately 50% of individuals who undergo total SDT respond with positive mood improvements the following day.8 However, effects can vary based on depressive severity, and clinical guidelines remain unclear.
Researchers have concluded that SDT is likely most effective when combined with other treatments.1 Other chronotherapeutic treatments include sleep phase advance, which shifts circadian rhythm, so individuals wake up and go to bed earlier than usual. Researchers observed that an advanced sleep phase is often a byproduct of bright light therapy. However, current data suggest that sleep phase advance can be used along with SDT to prolong the effectiveness of both treatments.
Combining various treatments appears to offer promising results. In a study that administered bright light therapy following partial sleep deprivation, groups treated with bright light therapy experienced more symptom relief when compared with controls.9 Sleep phase advance and bright light therapy following SDT are also shown to decrease depressive scores and increase remission rates significantly. Researchers have also revealed a decrease in suicidal ideation after this type of multipronged treatment.10
These results suggest that combining chronotherapy treatments may be an effective method for producing longer-lasting symptom relief in individuals with depression. Further, bright light therapy offers excellent drug-free treatment options for groups who cannot tolerate antidepressant medications. Both bright light therapy and chronotherapies appear to have fewer side effects than antidepressant medications and may induce more rapid results.
However, according to researchers, until randomized controlled research is performed, the true benefits of these treatments remain unclear; further, more research is needed to standardize treatment guidelines, including the optimal time, duration, and combination of bright light therapy.
1. Cunningham JEA, Stamp JA, Shapiro CM. Sleep and major depressive disorder: a review of non-pharmacological chronotherapeutic treatments for unipolar depression. Sleep Med. 2019;61:6-18.
2. Franzen PL, Buysse DJ. Sleep disturbances and depression: risk relationships for subsequence depression and therapeutic implications. Dialogues Clin Neurosci. 2008; 10(4):473-481.
3. aan het Rot M, Moskowitz DS, Young SN. Exposure to bright light is associated with positive social interaction and good mood over short time periods: a naturalistic study in mildly seasonal people. J Pyschiatr Res. 2008;42(4):311-319.
4. Levitt AJ, Joffe RT, Kennedy SH. Bright light augmentation in antidepressant nonresponders. J Clin Pyschiatr. 1991;52(8):336-337.
5. Schuchardt HM, Kasper S, Ruhrmann S. Is light therapy able to enhance the antidepressant effect of fluoxetine in patients with nonseasonal major depression? Pharmacopsychiatry. 1993;26-201.
6. Lam RW, Levitt AJ, Levitan RD, et al. Efficacy of bright light treatment, fluoxetine, and the combination in patients with nonseasonal major depressive disorder: a randomized controlled trial. JAMA Psychiatry. 2016;73(1):56-63.
7. Steffens DC, Fisher GG, Langa KM, Potter GG, Plassman BL. Prevalence of depression among older Americans: the aging, demographics, and memory study. Int Psychogeriatr. 2009;21(5):879-888.
8. Wu JC, Bunney WE. The biological basis of an antidepressant response to sleep deprivation and relapse: review and hypothesis. Am J Psychiatry. 1990;147(1):14-21.
9. Moscovici L, Kotler M. A multistage chronobiologic intervention for the treatment of depression: a pilot study. J Affect Disord. 2009;116(3):201-207.
10. Sahlem GL, Kalivas B, Fox JB, et al. Adjunctive triple chronotherapy (combined total sleep deprivation, sleep phase advance, and bright light therapy) rapidly improved mood and suicidality in suicidal depressed inpatients: an open label pilot study. J Psychiatr Res. 2014;59:101-107.