title: Evidence of a biological effect of light therapy on the retina of patients with seasonal affective disorder.
abstract: BACKGROUND
  Retinal sensitivity anomalies have been reported in patients affected by seasonal affective disorder (SAD). We used the electroretinogram (ERG) to assess seasonal change in retinal function in patients with SAD and healthy participants, as well as in patients following 4 weeks of light therapy.
  
  
  METHODS
  ERG assessments were obtained in 22 SAD patients (2 men, 20 women, mean age 31 +/- 9 years) in the fall/winter season before and after 2 and 4 weeks of light therapy and in summertime. Matched healthy participants (2 men, 14 women; mean age 29 +/- 8 years) were evaluated once in the fall/winter and once in summer. The 29-item Structured Interview Guide for the Hamilton Depression Rating Scale, Seasonal Affective Disorder version was administered. Standard ERG parameters were derived from the photopic and scotopic luminance response functions. Salivary melatonin concentration during ERG was assessed in both groups but during fall/winter assessments only.
  
  
  RESULTS
  A significantly lower cone ERG maximal amplitude and lower rod sensitivity was found in SAD patients before light therapy compared with healthy participants. Following 4 weeks of light therapy, a normalization of cone and rod ERG function occurred. ERG parameters in the summer and melatonin concentrations in fall/winter were not significantly different between groups.
  
  
  CONCLUSIONS
  Depressed patients with SAD demonstrate ERG changes in the winter compared with healthy comparison subjects with lower rod retinal sensitivity and lower cone maximal amplitude. These changes normalized following 4 weeks of light therapy and during the summer, suggesting that ERG changes are state markers for SAD.
authors.affiliation: Centre de recherche Université Laval Robert-Giffard, Centre hospitalier de l'Université Laval, Quebec G1J 2G3, Canada.
authors.forename: Marie-Pier
authors.initials: MP
authors.lastname: Lavoie
authors.forename: Raymond W
authors.initials: RW
authors.lastname: Lam
authors.forename: Guylain
authors.initials: G
authors.lastname: Bouchard
authors.forename: Alexandre
authors.initials: A
authors.lastname: Sasseville
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Charron
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Gagné
authors.forename: Philippe
authors.initials: P
authors.lastname: Tremblay
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Filteau
authors.forename: Marc
authors.initials: M
authors.lastname: Hébert
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D004596:Electroretinography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008875:Middle Aged; D010789:Phototherapy; D012160:Retina / Q000503:physiopathology*; D016574:Seasonal Affective Disorder / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D012621:Seasons; D013997:Time Factors; D055815:Young Adult
chemical_list: D008550:Melatonin