title: Effects of selective serotonin reuptake inhibitor treatment on plasma oxytocin and cortisol in major depressive disorder.
abstract: BACKGROUND
  Oxytocin is known for its capacity to facilitate social bonding, reduce anxiety and for its actions on the stress hypothalamopituitary adrenal (HPA) axis. Since oxytocin can physiologically suppress activity of the HPA axis, clinical applications of this neuropeptide have been proposed in conditions where the function of the HPA axis is dysregulated. One such condition is major depressive disorder (MDD). Dysregulation of the HPA system is the most prominent endocrine change seen with MDD, and normalizing the HPA axis is one of the major targets of recent treatments. The potential clinical application of oxytocin in MDD requires improved understanding of its relationship to the symptoms and underlying pathophysiology of MDD. Previous research has investigated potential correlations between oxytocin and symptoms of MDD, including a link between oxytocin and treatment related symptom reduction. The outcomes of studies investigating whether antidepressive treatment (pharmacological and non-pharmacological) influences oxytocin concentrations in MDD, have produced conflicting outcomes. These outcomes suggest the need for an investigation of the influence of a single treatment class on oxytocin concentrations, to determine whether there is a relationship between oxytocin, the HPA axis (e.g., oxytocin and cortisol) and MDD. Our objective was to measure oxytocin and cortisol in patients with MDD before and following treatment with selective serotonin reuptake inhibitors, SSRI.
  
  
  METHODS
  We sampled blood from arterial plasma. Patients with MDD were studied at the same time twice; pre- and post- 12 weeks treatment, in an unblinded sequential design (clinicaltrials.govNCT00168493).
  
  
  RESULTS
  Results did not reveal differences in oxytocin or cortisol concentrations before relative to following SSRI treatment, and there were no significant relationships between oxytocin and cortisol, or these two physiological variables and psychological symptom scores, before or after treatment.
  
  
  CONCLUSIONS
  These outcomes demonstrate that symptoms of MDD were reduced following effective treatment with an SSRI, and further, stress physiology was unlikely to be a key factor in this outcome. Further research is required to discriminate potential differences in underlying stress physiology for individuals with MDD who respond to antidepressant treatment, relative to those who experience treatment resistance.
authors.affiliation: Monash Alfred Psychiatry Research Centre, Central Clinical School, Monash University and The Alfred, Melbourne, Australia. ckeating@swin.edu.au
authors.forename: Charlotte
authors.initials: C
authors.lastname: Keating
authors.forename: Tye
authors.initials: T
authors.lastname: Dawood
authors.forename: David A
authors.initials: DA
authors.lastname: Barton
authors.forename: Gavin W
authors.initials: GW
authors.lastname: Lambert
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Tilbrook
mesh_terms: D000328:Adult; D000368:Aged; D001007:Anxiety / Q000097:blood / Q000150:complications; D003865:Major Depressive Disorder / Q000097:blood* / Q000150:complications / Q000188:drug therapy*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010121:Oxytocin / Q000097:blood*; D017367:Selective Serotonin Reuptake Inhibitors / Q000627:therapeutic use*
chemical_list: D006854:Hydrocortisone; D010121:Oxytocin; D017367:Selective Serotonin Reuptake Inhibitors