title: Interaction between 5-HTTLPR genotype and cognitive stress vulnerability on sleep quality: effects of sub-chronic tryptophan administration.
abstract: BACKGROUND
  Abundant evidence suggests that allelic variation in the serotonin transporter-linked polymorphic region (5-HTTLPR) influences susceptibility to stress and its affective consequences due to brain serotonergic vulnerability. Based on recent assumptions, the present study examined whether the 5-HTTLPR genotype may also interact with a vulnerability to chronic stress experience (conceptualized by trait neuroticism) in order to influence sleep quality and, additionally, whether this is influenced by brain serotonergic manipulations.
  
  
  METHODS
  In a well-balanced experimental design, homozygous S-allele (n = 57) and L-allele (n = 54) genotypes with high and low chronic stress vulnerability (neuroticism) were first assessed for general past sleep quality during a month before onset of the experiment. Then subjects were assessed for sleep quality following 7 days of tryptophan (3.0g/day) or placebo intake.
  
  
  RESULTS
  Although high neuroticism was significantly related to a higher frequency of stressful life events and daily hassles, it did not interact with the 5-HTTLPR genotype on general past sleep quality. However, as expected, a 7 day period of tryptophan administration was exclusively associated with better sleep quality scores in the S'/S' genotype with high trait neuroticism.
  
  
  CONCLUSIONS
  Current findings suggest that 5-HTTLPR does not directly interact with stress vulnerability in order to influence sleep quality. Instead, based on current and previous findings, it is suggested that the S'/S' 5-HTTLPR genotype promotes the risk for stress-related sleep disturbances because of an increased susceptibility to the depressogenic consequences of stress. Accordingly, by way of reducing depressive symptomatology, tryptophan augmentation may particularly improve sleep quality in stress-vulnerable individuals carrying the 5-HTTLPR S-allele.
authors: Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University.
authors: Jens H
authors: JH
authors: van Dalfsen
authors: Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University. r.markus@maastrichtuniversity.nl.
authors: C Rob
authors: CR
authors: Markus
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D018687:Antidepressive Agents, Second-Generation / Q000008:administration & dosage*; D001008:Anxiety Disorders / Q000178:diet therapy / Q000235:genetics / Q000523:psychology; D004311:Double-Blind Method; D005260:Female; D005838:Genotype; D006801:Humans; D008016:Life Change Events; D008297:Male; D000075384:Neuroticism; D010555:Personality Inventory; D011569:Psychiatric Status Rating Scales; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D012893:Sleep Wake Disorders / Q000209:etiology* / Q000235:genetics; D014364:Tryptophan / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D018687:Antidepressive Agents, Second-Generation; D050486:Serotonin Plasma Membrane Transport Proteins; D014364:Tryptophan
keywords: 5-HTTLPR; depression; sleep; stress; tryptophan
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