title: The effects of low-intensity narrow-band blue-light treatment compared to bright white-light treatment in sub-syndromal seasonal affective disorder.
abstract: BACKGROUND
  The discovery of a novel photoreceptor in the retinal ganglion cells with a highest sensitivity of 470-490 nm blue light has led to research on the effects of short-wavelength light in humans. Several studies have explored the efficacy of monochromatic blue or blue-enriched light in the treatment of SAD. In this study, a comparison has been made between the effects of broad-wavelength light without ultraviolet (UV) wavelengths compared to narrow-band blue light in the treatment of sub-syndromal seasonal affective disorder (Sub-SAD).
  
  
  METHODS
  In a 15-day design, 48 participants suffering from Sub-SAD completed 20-minute sessions of light treatment on five consecutive days. 22 participants were given bright white-light treatment (BLT, broad-wavelength light without UV 10 000 lux, irradiance 31.7 Watt/m(2)) and 26 participants received narrow-band blue light (BLUE, 100 lux, irradiance 1.0 Watt/m(2)). All participants completed daily and weekly questionnaires concerning mood, activation, sleep quality, sleepiness and energy. Also, mood and energy levels were assessed by means of the SIGH-SAD, the primary outcome measure.
  
  
  RESULTS
  On day 15, SIGH-SAD ratings were significantly lower than on day 1 (BLT 54.8 %, effect size 1.7 and BLUE 50.7 %, effect size 1.9). No statistically significant differences were found on the main outcome measures.
  
  
  CONCLUSIONS
  Light treatment is an effective treatment for Sub-SAD. The use of narrow-band blue-light treatment is equally effective as bright white-light treatment.
  
  
  BACKGROUND
  This study was registered in the Dutch Trial Register (Nederlands Trial Register TC =  4342 ) (20-12-2013).
authors.affiliation: University of Groningen, University Medical Center Groningen, University Center for Psychiatry, PO Box 30001, Groningen, 9700 RB, The Netherlands. y.meesters@umcg.nl.
authors.forename: Ybe
authors.initials: Y
authors.lastname: Meesters
authors.affiliation: University of Groningen, University Medical Center Groningen, University Center for Psychiatry, PO Box 30001, Groningen, 9700 RB, The Netherlands. w.h.winthorst@umcg.nl.
authors.forename: Wim H
authors.initials: WH
authors.lastname: Winthorst
authors.affiliation: University of Groningen, University Medical Center Groningen, University Center for Psychiatry, PO Box 30001, Groningen, 9700 RB, The Netherlands. wianneduijzer@gmail.com.
authors.forename: Wianne B
authors.initials: WB
authors.lastname: Duijzer
authors.affiliation: Philips Consumer Lifestyle Drachten, Drachten, The Netherlands. vanja.hommes@philips.com.
authors.forename: Vanja
authors.initials: V
authors.lastname: Hommes
mesh_terms: D000328:Adult; D000339:Affect / Q000528:radiation effects; D005260:Female; D006801:Humans; D007406:Interview, Psychological / Q000379:methods; D008027:Light; D008297:Male; D008875:Middle Aged; D010789:Phototherapy / Q000295:instrumentation / Q000379:methods; D016574:Seasonal Affective Disorder / Q000175:diagnosis / Q000628:therapy; D012894:Sleep Stages / Q000528:radiation effects; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome