title: A deficit in peripheral serotonin levels in major depressive disorder but not in chronic widespread pain.
abstract: OBJECTIVE
  It has been proposed that serotonin dysfunctions underlie the pathophysiology of various mood disorders (including major depressive disorder, MDD) and chronic pain conditions characterized by deficient pain inhibition, such as fibromyalgia (FM). There is reliable data showing that serotonin disturbances are involved in the pathophysiology of MDD. However, in the case of FM, results published so far are less consistent. Therefore, the current cross-sectional study sought to measure plasma serotonin levels in FM patients, MDD patients, and healthy controls (HC).
  
  
  METHODS
  Twenty-nine FM patients, 17 MDD patients, and 57 HC were recruited who did not differ in terms of age, sex, and the presence or absence of a regular menstrual cycle. Plasma samples were analysed with mass spectrometry.
  
  
  RESULTS
  Serotonin levels were decreased in MDD patients, relative to FM patients and HC. Post hoc analyses showed that serotonin levels were decreased in FM patients taking antidepressants, relative to HC, but not in drug-free FM patients. Moreover, serotonin levels were negatively correlated with mood symptoms across groups.
  
  
  CONCLUSIONS
  Our results further confirm that MDD is associated with decreased serotonin levels, but that serotonin levels are not altered in FM per se, and suggest that 5-Hydroxytryptamine is related to mood symptoms in these patient groups. Our results also suggest that the taking of antidepressant is a major confound to consider when studying serotonin functioning in FM. The long-term use of antidepressants in FM may lead to serotonin depletion. Conversely, serotonin depletion may be before the taking of antidepressants in FM.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Canada.
authors.forename: Emilie
authors.initials: E
authors.lastname: Paul-Savoie
authors.forename: Stéphane
authors.initials: S
authors.lastname: Potvin
authors.forename: Kathya
authors.initials: K
authors.lastname: Daigle
authors.forename: Edith
authors.initials: E
authors.lastname: Normand
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Corbin
authors.forename: René
authors.initials: R
authors.lastname: Gagnon
authors.forename: Serge
authors.initials: S
authors.lastname: Marchand
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000097:blood*; D005260:Female; D005356:Fibromyalgia / Q000097:blood*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000097:blood* / Q000503:physiopathology; D017288:Pain Threshold / Q000502:physiology; D012701:Serotonin / Q000097:blood*
chemical_list: D015415:Biomarkers; D012701:Serotonin