title: The effects of blue-enriched light treatment compared to standard light treatment in Seasonal Affective Disorder.
abstract: BACKGROUND
  One of the most frequently investigated hypotheses of the pathophysiology underlying Seasonal Affective Disorder (SAD) is a disturbance of circadian rhythms. Since the circadian system as well as other non-visual effects is especially sensitive to blue light, a new light therapy device with blue enriched polychromatic light was tested for its efficacy to treat SAD.
  
  
  METHODS
  Within one winter 52 patients were treated in one of three conditions: 30 min full spectrum light (9000 lx, 5000 K), 30 min blue-enriched light (9000 lx, 17,000 K), or 20 min blue-enriched light. The study lasted 22 days with 10 days of morning-light treatment on weekdays during the first 2 weeks.
  
  
  RESULTS
  Depressive symptoms (SIGH SAD) diminished over the 3-week period in all conditions, with no significant differences between conditions. The percentage responders were high, differing from 75%, 59% and 71% for the standard-LT, 30 min blue-enriched-LT, and 20 min blue-enriched-LT, respectively.
  
  
  CONCLUSIONS
  The lack of superiority of high intensity blue-enriched light over standard bright light treatment does not clearly support nor rule out the possibility of an important role for the circadian system or the blue sensitive non-visual image forming system in general, in the pathophysiology of SAD. The lack of a difference between conditions may also be the result of a saturated response to the high light intensities used. Recent data indeed suggest that low intensity blue-enriched light may be as effective as standard bright light treatment. The possibility of improving light therapy for SAD patients by applying light of shorter duration or at lower light intensities is highly relevant for optimizing treatment and will help to clarify the role of the circadian system and/or the non-image forming photoreceptors in SAD pathophysiology.
  
  
  BACKGROUND
  https://register.clinicaltrials.gov: NCT01048294.
authors.affiliation: Department of Psychiatry, University Medical Center Groningen, The Netherlands. Electronic address: m.c.m.gordijn@rug.nl.
authors.forename: M C M
authors.initials: MCM
authors.lastname: Gordijn
authors.affiliation: Department of Psychiatry, University Medical Center Groningen, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: 't Mannetje
authors.affiliation: Department of Psychiatry, University Medical Center Groningen, The Netherlands.
authors.forename: Y
authors.initials: Y
authors.lastname: Meesters
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010789:Phototherapy / Q000379:methods*; D016574:Seasonal Affective Disorder / Q000503:physiopathology / Q000628:therapy*; D055815:Young Adult