title: The use of ketamine as an antidepressant: a systematic review and meta-analysis.
abstract: OBJECTIVE
  The current meta-analysis examines the effects of ketamine infusion on depressive symptoms over time in major depressive disorder (MDD) and bipolar disorder (BD).
  
  
  METHODS
  Following a systematic review of the literature, data were extracted from 21 studies (n = 437 receiving ketamine) and analysed at four post-infusion time points (4 h, 24 h, 7 days and 12-14 days). The moderating effects of several factors were assessed including: repeat/single infusion, diagnosis, open-label/participant-blind infusion, pre-post/placebo-controlled design and the sex of patients.
  
  
  RESULTS
  Effect sizes were significantly larger for repeat than single infusion at 4 h, 24 h and 7 days. For single infusion studies, effect sizes were large and significant at 4 h, 24 h and 7 days. The percentage of males was a predictor of antidepressant response at 7 days. Effect sizes for open-label and participant-blind infusions were not significantly different at any time point.
  
  
  CONCLUSIONS
  Single ketamine infusions elicit a significant antidepressant effect from 4 h to 7 days; the small number of studies at 12-14 days post infusion failed to reach significance. Results suggest a discrepancy in peak response time depending upon primary diagnosis - 24 h for MDD and 7 days for BD. The majority of published studies have used pre-post comparison; further placebo-controlled studies would help to clarify the effect of ketamine over time.
authors.affiliation: School of Life and Medical Sciences, University of Hertfordshire, Hatfield, UK.
authors.forename: Caoimhe M
authors.initials: CM
authors.lastname: Coyle
authors.forename: Keith R
authors.initials: KR
authors.lastname: Laws
mesh_terms: D000928:Antidepressive Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000188:drug therapy*; D003865:Major Depressive Disorder / Q000188:drug therapy*; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007649:Ketamine / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D012737:Sex Factors; D013997:Time Factors
chemical_list: D000928:Antidepressive Agents; D018691:Excitatory Amino Acid Antagonists; D007649:Ketamine
keywords: bipolar disorder; depression; ketamine; major depressive disorder