title: Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis.
abstract: OBJECTIVE
  To review the literature regarding the effectiveness of 5-hydroxytryptophan (5-HT) and L-tryptophan in the treatment of unipolar depression.
  
  
  METHODS
  A systematic review of the literature from 1966 to 2000 using the search terms 'tryptophan', 5-hydroxytryptophan', '5-HTP', '5-HT' and 'depression'. We extracted and grouped data for meta-analysis by pooling odds ratios (OR) and relative risks where possible.
  
  
  RESULTS
  One hundred and eight studies were located of which only two studies, one of 5-HT and one of L-tryptophan, with a total of 64 patients met sufficient quality criteria to be included. These studies suggest 5-HT and L-tryptophan are better than placebo at alleviating depression (Peto OR = 4.1, 95% CI = 1.3-13.2). However, the small size of the studies, and the large number of inadmissible, poorly executed studies, casts doubt on the result from potential publication bias, and suggests that they are insufficiently evaluated to assess their effectiveness.
  
  
  CONCLUSIONS
  A large body of evidence was subjected to very basic criteria for assessing reliability and validity, and was found to largely be of insufficient quality to inform clinical practice. More well-designed studies are urgently required to enable an assessment of what may be an effective class of agents.
authors.affiliation: School of Population Health, Department of Public Health, University of Queensland Medical School, Herston 4006, Australia. k.shaw@sph.uq.edu.au
authors.forename: Kelly
authors.initials: K
authors.lastname: Shaw
authors.forename: Jane
authors.initials: J
authors.lastname: Turner
authors.forename: Christopher
authors.initials: C
authors.lastname: Del Mar
mesh_terms: D006916:5-Hydroxytryptophan / Q000009:adverse effects / Q000627:therapeutic use*; D003866:Depressive Disorder / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome; D014364:Tryptophan / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D014364:Tryptophan; D006916:5-Hydroxytryptophan