title: The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality.
abstract: BACKGROUND
  Conflicting results have been reported in previous association studies of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR), seasonal affective disorder (SAD) and seasonality (seasonal variations in mood and behaviour). The aim of this study was to test for association in new case-control and population-based materials, and to perform a combined analysis of all published studies of 5-HTTLPR and SAD.
  
  
  METHODS
  One hundred and forty-seven new SAD cases and 115 controls were genotyped for 5-HTTLPR and in total 464 patients and 414 controls were included in the pooled analysis. In addition, 226 individuals selected for unusually high or low seasonality scores from a population based material and 46 patients with non-seasonal depression were analysed. Different genetic models were tested and seasonality was analysed both as a qualitative (high v. low) and as a quantitative trait in the different sample sets.
  
  
  RESULTS
  No association between 5-HTTLPR and SAD was found in the new case-control material, in the combined analysis of all samples, or when only including 316 patients with controls (N = 298) selected for low seasonality. A difference was detected between the population based high and low seasonality groups, when assuming a recessive effect of the short allele (20% and 10% short allele homozygotes, respectively, OR (95% CI): 2.24 (1.03-4.91)). Quantitative analysis of seasonality revealed no association with 5-HTTLPR in any sample set.
  
  
  CONCLUSIONS
  These results do not suggest a major role of the short variant of 5-HTTLPR in susceptibility to SAD, but provide modest evidence for an effect on seasonality.
authors.affiliation: Department of Molecular Medicine, Karolinska Institute and Karolinska Hospital, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Johansson
authors.forename: M
authors.initials: M
authors.lastname: Willeit
authors.forename: R
authors.initials: R
authors.lastname: Levitan
authors.forename: T
authors.initials: T
authors.lastname: Partonen
authors.forename: C
authors.initials: C
authors.lastname: Smedh
authors.forename: J
authors.initials: J
authors.lastname: Del Favero
authors.forename: S
authors.initials: S
authors.lastname: Bel Kacem
authors.forename: N
authors.initials: N
authors.lastname: Praschak-Rieder
authors.forename: A
authors.initials: A
authors.lastname: Neumeister
authors.forename: M
authors.initials: M
authors.lastname: Masellis
authors.forename: V
authors.initials: V
authors.lastname: Basile
authors.forename: P
authors.initials: P
authors.lastname: Zill
authors.forename: B
authors.initials: B
authors.lastname: Bondy
authors.forename: T
authors.initials: T
authors.lastname: Paunio
authors.forename: S
authors.initials: S
authors.lastname: Kasper
authors.forename: C
authors.initials: C
authors.lastname: Van Broeckhoven
authors.forename: L G
authors.initials: LG
authors.lastname: Nilsson
authors.forename: R
authors.initials: R
authors.lastname: Lam
authors.forename: M
authors.initials: M
authors.lastname: Schalling
authors.forename: R
authors.initials: R
authors.lastname: Adolfsson
mesh_terms: D000328:Adult; D000339:Affect; D002352:Carrier Proteins / Q000235:genetics*; D016022:Case-Control Studies; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D026901:Membrane Transport Proteins; D008875:Middle Aged; D009419:Nerve Tissue Proteins; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D016574:Seasonal Affective Disorder / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism; D012621:Seasons; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin