This article is part of the 2018 NMJ Oncology Special Issue. Download the full issue.
Kirschbaum-Lesch I, Gest S, Legenbauer T, Holtmann M. Feasibility and efficacy of bright-light therapy in depressed adolescent inpatients. Z Kinder Jugendpsychiatr Psychother. 2018;46(5):423-429.
Open-label, single-arm, prospective clinical trial
To assess extended use (4 weeks) of blue light therapy (BLT) glasses on several measures of depression in teenage inpatients and compare the outcomes of BLT glasses to a prior study at the same institution that used a bright light therapy box for 2 weeks in a similar population.
Thirty-nine teenagers (32 female, 7 male, aged 12-18 years) admitted to the hospital for at least 4 weeks with moderate to severe depression were enrolled. Depression was defined by the Beck Depression Inventory II (BDI-II), a 21-item self-assessment questionnaire for depressed mood over the past 2 weeks. Thirty-two participants indicated “severe depressive symptoms” according to BDI-II scores.
Bright light therapy was administered in addition to treatment as usual (TAU). This treatment was unspecified, but 36% of the participants received pharmacological antidepressant therapy.
Exclusion criteria included diagnosis of schizophrenia; symptoms of psychosis or suicidal tendencies; treatment with antipsychotics or beta blockers; pregnancy; hypersensitivity to light; and eye disease.
Comparator group from prior study (n=39) at the same institution using blue light box therapy had no significant differences in age, gender, antidepressant use, or baseline BDI-II scores.
Participants received 4 weeks of BLT via bright light glasses (brand name Luminette) each weekday for 30 minutes in the morning. The glasses provided 10,000 lux of blue light directed toward the bottom of the eyes, which allowed participants to go about their normal morning activities.
Study Parameters Assessed
Participants were assessed at the start of the trial (T1), 2 weeks into the trial (T2), at the end of the 4-week intervention (T3), and 2 weeks after the conclusion of the trial (T4) for the following objective and subjective measures:
- Depression, as determined by the BDI-II
- Sleep, as evaluated by the Schlaffragebogen B revised (SF-BR), a 31-item questionnaire to determine the quality and restorative nature of sleep
- Chronotype, as determined by the Morningness-Eveningness Questionnaire (D-MEQ), a 15-item questionnaire that assesses circadian preference and phase shift
- Global severity of symptoms and overall change throughout the study, as determined by the Clinical Global Impressions (CGI) scale, completed by the therapist.
The previous study used a light box that provided 10,000 lux of white light. This intensity is comparable to sunlight 40 minutes after sunrise.
Primary Outcome Measures
Effectiveness of the blue light therapy glasses on subjective and objective measures listed above; comparison to historical data of a 2-week trial at the same institution using a light box with equivalent lux.
The BDI-II results improved from the beginning to the end of the study (T1 to T4), with statistically significant change between T1 and T2. Clinical Global Impressions scores were significantly improved between T2-T4 and T3-T4. Sleep improved from the start of the study (T1) to week 4 (T3). Chronotype did not change significantly.
The hypothesis that a longer duration (4 weeks) of BLT may have better effects than 2 weeks’ duration was disproven in this study. Depression and sleep were no different at 4 weeks (T3) with the use of BLT glasses for 4 weeks vs BLT boxes for 2 weeks.
It has been well-established that BLT can be useful for treating seasonal and nonseasonal depression.1-3 Especially in places with low light throughout the winter months, light boxes have become more and more popular. This study specifically compares the efficacy of a new type of treatment device, light “glasses,” to the more widely available light boxes. The light glasses are worn like regular glasses but have a sort of visor that comes out an inch or so from the face and shines a light down over the eyes. The disadvantage of a light box is that the user must remain stationary and is asked to look directly at the light box a few times during the treatment. The light glasses emit light that encompasses the lower half of the eye without needing to look directly into the light. This allows a person to go about his or her normal morning routine while using them, which could potentially increase compliance.
This study is interesting because it offers a simple tool to help depressed teens improve mood with a very low-force intervention. Another intriguing finding is that the efficacy of BLT glasses peaked after 2 weeks. Extending the treatment to 4 weeks did not show further improvement, so it appears that BLT treatments quickly affect underlying pathophysiology and there is a sustaining quality to this change.
The light glasses emit light that encompasses the lower half of the eye without needing to look directly into the light. This allows a person to go about his or her normal morning routine while using them, which could potentially increase compliance.
Would exposure to natural sunlight have similar effects? Several studies looked at reported sun exposure and found that it is inversely correlated with depressive symptoms, but a PubMed search failed to find any studies that directly compare sunlight vs bright light therapy.4-6 Perhaps in the context of an inpatient facility, light box or light glasses are easier to control than outdoor light exposure, from a study design perspective. However, it would be useful to know if there are unique antidepressive effects to BLT as glasses or box vs sending the affected teen outside for 30 minutes of unshaded sun exposure each day.
One interesting difference between the light boxes and glasses is the type of light emitted. Light boxes use white light, and the glasses use blue light only. Both emit the same intensity of light, 10,000 lux, which approximates the intensity of sunlight 40 minutes after sunrise. Wavelengths from the blue portion of the visible spectrum, however, are the most potent regulator of circadian rhythm and more closely approximate the stimulation one feels from sunlight.7 Blue light decreases the release of melatonin, which can increase wakefulness. Conversely, blue light–blocking glasses worn for 3 hours before bedtime significantly decrease the amount of time it takes to go to sleep and improve the overall restfulness of sleep.8
It makes sense that exposing the body to natural light and dark cycles will help to regulate and enhance the quality of sleep, but how does this impact mood? Is disruption in sleep causing depression, is depression causing disruption in sleep, or are they concurrent features of the same process? Participants in this study all took a morningness-eveningness questionnaire and none of them were determined to be strongly morning people. Eveningness is generally associated with depression, particularly in adolescents.9-12 So we see that disrupted circadian rhythm and sleep/wake cycles are associated with depression, but what happens physiologically with exposure to light that helps to improve mood?
From a biochemical perspective, several neurotransmitters are responsive to light and dark cycles. Melatonin, serotonin, dopamine, and norepinephrine all respond to BLT. Melatonin, dopamine, and serotonin are all produced in the retina. Retinal dopamine production is stimulated by BLT; conversely, dopamine deficiency is associated with symptoms of depression.13-14 Blue light therapy also suppresses the production of retinal melatonin, and blue light–blocking glasses stimulate melatonin production. In normal circumstances, melatonin is highest at night and during sleep. People with sleep disorders and depression exhibit disruption in the normal circadian levels of plasma melatonin.15-16
Tryptophan, serotonin, and catecholamines such as dopamine and norepinephrine are also implicated in the relationship between light exposure and symptoms of depression. Several studies have utilized tryptophan depletion to induce a relapse in depressive symptoms in patients who are in a BLT-induced stable remission.17-19 Tryptophan depletion is achieved by feeding patients a tryptophan-free amino acid blend, limiting the substrate needed for production to 5-HTP (hydroxytryptophan) and subsequent serotonin production. Secretion of serotonin is then reduced even with bright light treatment, which causes the resurgence in depressive symptoms.20 Similar studies show the return of depressed symptoms with catecholamine depletion.
This study highlights the fascinating interplay between light and dark cycles and our internal circadian rhythm. Being awake and exposed to morning sunlight initiates the release of neurotransmitters that improve energy and mood during the day. Conversely, dim light and darkness encourage melatonin to help calm the brain and initiate restful sleep. By using a simple, low-force intervention to replicate morning sunlight we can help patients improve mood and sleep.