Brenda Byrne

Light therapy for seasonal affective disorder with blue narrow-band light-emitting diodes (LEDs).

BACKGROUND While light has proven an effective treatment for Seasonal Affective Disorder (SAD), an optimal wavelength combination has not been determined. Short wavelength light (blue) has demonstrated potency as a stimulus for acute melatonin suppression and circadian phase shifting. METHODS This study tested the efficacy of short wavelength light therapy for SAD. Blue light emitting diode (LED) units produced 468 nm light at 607 microW/cm2 (27 nm half-peak bandwidth); dim red LED units provided 654 nm at 34 microW/cm2 (21 nm half-peak bandwidth). Patients with major depression with a seasonal pattern, a score of > or =20 on the Structured Interview Guide for the Hamilton Depression Rating Scale-SAD version (SIGH-SAD) and normal sleeping patterns (routine bedtimes between 10:00 pm and midnight) received 45 minutes of morning light treatment daily for 3 weeks. Twenty-four patients completed treatment following random assignment of condition (blue vs. red light). The SIGH-SAD was administered weekly. RESULTS Mixed-effects analyses of covariance determined that the short wavelength light treatment decreased SIGH-SAD scores significantly more than the dimmer red light condition (F = 6.45, p = .019 for average over the post-treatment times). CONCLUSIONS Narrow bandwidth blue light at 607 microW/cm2 outperforms dimmer red light in reversing symptoms of major depression with a seasonal pattern.

Sensitivity of the Human Circadian System to Short-Wavelength (420-nm) Light

The circadian and neurobehavioral effects of light are primarily mediated by a retinal ganglion cell photoreceptor in the mammalian eye containing the photopigment melanopsin. Nine action spectrum studies using rodents, monkeys, and humans for these responses indicate peak sensitivities in the blue region of the visible spectrum ranging from 459 to 484 nm, with some disagreement in short-wavelength sensitivity of the spectrum. The aim of this work was to quantify the sensitivity of human volunteers to monochromatic 420-nm light for plasma melatonin suppression. Adult female (n = 14) and male (n = 12) subjects participated in 2 studies, each employing a within-subjects design. In a fluence-response study, subjects (n = 8) were tested with 8 light irradiances at 420 nm ranging over a 4-log unit photon density range of 1010 to 1014 photons/cm 2/sec and 1 dark exposure control night. In the other study, subjects (n = 18) completed an experiment comparing melatonin suppression with equal photon doses (1.21 × 1013 photons/cm2/sec) of 420 nm and 460 nm monochromatic light and a dark exposure control night. The first study demonstrated a clear fluence-response relationship between 420-nm light and melatonin suppression (p < 0.001) with a half-saturation constant of 2.74 × 1011 photons/cm2/sec. The second study showed that 460-nm light is significantly stronger than 420-nm light for suppressing melatonin (p < 0.04). Together, the results clarify the visible short-wavelength sensitivity of the human melatonin suppression action spectrum. This basic physiological finding may be useful for optimizing lighting for therapeutic and other applications.

Short-wavelength enrichment of polychromatic light enhances human melatonin suppression potency.

The basic goal of this research is to determine the best combination of light wavelengths for use as a lighting countermeasure for circadian and sleep disruption during space exploration, as well as for individuals living on Earth. Action spectra employing monochromatic light and selected monochromatic wavelength comparisons have shown that short‐wavelength visible light in the blue‐appearing portion of the spectrum is most potent for neuroendocrine, circadian, and neurobehavioral regulation. The studies presented here tested the hypothesis that broad spectrum, polychromatic fluorescent light enriched in the short‐wavelength portion of the visible spectrum is more potent for pineal melatonin suppression in healthy men and women. A total of 24 subjects were tested across three separate experiments. Each experiment used a within‐subjects study design that tested eight volunteers to establish the full‐range fluence–response relationship between corneal light irradiance and nocturnal plasma melatonin suppression. Each experiment tested one of the three types of fluorescent lamps that differed in their relative emission of light in the short‐wavelength end of the visible spectrum between 400 and 500 nm. A hazard analysis, based on national and international eye safety criteria, determined that all light exposures used in this study were safe. Each fluence–response curve demonstrated that increasing corneal irradiances of light evoked progressively increasing suppression of nocturnal melatonin. Comparison of these fluence–response curves supports the hypothesis that polychromatic fluorescent light is more potent for melatonin regulation when enriched in the short‐wavelength spectrum.

Treatment of winter depression with a portable, head-mounted phototherapy device

1. A portable, head-mounted device was developed for administration of light therapy. A randomized crossover protocol was used to test the therapeutic efficacy of this device, compared to a standard light box, for treatment of winter depression. 2. Depressive symptoms were significantly reduced by both the head-mounted device and the light box. 3. Therapeutic efficacy of the two devices was not significantly different. 4. The head-mounted device was rated by patients as significantly more convenient than the conventional light box; this may be important in improving patient compliance.

Sleep patterns and dexamethasone suppression in nondepressed bulimics

In this study, we attempted to find markers of depression in bulimics without major depression or a history of anorexia nervosa and to examine cortisol suppression (DST) by bulimics following administration of dexamethasone

Light-induced plasma melatonin suppression in seasonal affective disorder

1. Subjects with seasonal affective disorder were exposed to 0, 500 and 1000 lux of white light for one hour beginning at 0300 hours. 2. Plasma samples were taken periodically and analysed for melatonin. 3. Plasma melatonin levels were suppressed by exposure to both 500 and 1000 lux light levels, suggesting that SAD patients show no neuroendocrine insensitivity to light but may show supersensitive responses to light.

Bright light imagery does not suppress melatonin

To the Editor: Studies using a wide range of species have shown that environmental light is the primary stimulus for regulating circadian rhythms, seasonal cycles and neuroendocrine responses [Wetterberg, 1993]. Research on humans has confirmed that presentation of light during the dark portion of the 24-hr cycle results in suppression of melatonin as measured in blood plasma and that melatonin suppression is a function of intensity, spectrum, timing and duration of exposure to light [Brainard et al., 1997]. Although light is the primary stimulus for regulating the circadian system, other non-photic stimuli such as social cues, sound, temperature, exercise and conditioned stimuli may also influence physiological timing functions [Lakin-Thomas, 1997]. In classical conditioning studies with rats, Golombek et al. [1994] entrained high melatonin levels in the presence of light using restricted water availability as the conditioned stimulus. Similarly, it has been shown that cellular and behavioral circadian phase shifting in rats can be elicited by neutral, non-photic stimuli when they have been paired with light stimuli in a classical conditioning paradigm [Amir and Stewart, 1996]. These animal studies have demonstrated that the circadian and neuroendocrine systems can be subjected to learning processes which can override the usual environmental signals by which these systems operate. In humans, mental imagery has been studied as a stimulus for a range of physiological responses, including heart rate, changes in auditory evoked potentials and motor cortex activation [Kunzendorf, 1990]. More specific to the visual system, vivid imagers have been found to experience afterimages of a fixed size on the retina and to produce evoked potentials in the optic tract which varied in amplitude as an imagined light was increased and then decreased in intensity [Kunzendorf, 1990]. These findings suggest the possibility that human subjects exposed to imagined light might be able to suppress high nocturnal levels of melatonin. If so, the role of higher processing in non-photic responses to bright light would require further elucidation; if not, a placebo-resistant element of the response of the human organism to light would be identified. To test the hypothesis that pineal regulation in humans is susceptible to cognition, two experiments were conducted to determine whether lightinduced melatonin suppression might be duplicated by bright light mental imagery. Subjects measuring high on scales of hypnotic susceptibility were chosen, as highly hypnotizable subjects engaged in mental imagery produce responses not found in those low in hypnotic susceptibility [Wallace 1980; Jenner et al., 1990]. In the first experiment, subjects were three healthy female volunteers, ages 28–32, who had received high scores (between 8 and 11 points) on the Stanford Hypnotic Susceptibility Scale: Form C [Weitzenhoffer and Hilgard, 1962]. Participants spent 3 nights, separated by at least 1 wk, in a sleep laboratory. On each night, blood (10 mL) was drawn from the antecubital vein through an intravenous catheter before and after a 50-min experimental manipulation (02:00 to 02:50) as follows: Night 1 — awake in darkness; Night 2 — awake and facing a fluorescent white light unit; Night 3 — awake in darkness during hypnotic induction and suggestions for bright light mental images provided by the author (BB). Plasma samples were stored at −20°C for radioimmunoassay (RIA). Light was provided by six fluorescent lamps (VitaLite, Duro-Test, North Bergen, NJ) in a 2×4 foot fixture with a UVT diffuser. Illuminance at subject’s cornea (3 feet from the light source) measured 2500 lux with a Minolta Chroma Meter (Minolta, Ltd., Osaka, Japan). In the second experiment, we increased the number of participants, made the delivery of the mental imagery condition more uniform, tracked subject alertness and compliance during the experimental procedures, and attempted to maximize ‘‘placebo’’ factors of understanding and motivation. Subjects were six healthy young adults, ages 21–28, whose scores were moderate to high on