title: Association of TPH-1 and TPH-2 gene polymorphisms with suicidal behavior: a systematic review and meta-analysis.
abstract: BACKGROUND
  It is widely acknowledged that suicidal behavior (SB) has a genetic influence. As a consequence, molecular genetic studies have been mostly conducted on serotonergic genes. One of the most promising candidate genes of this system is tryptophan hydroxylase (TPH). Although there have been several positive studies associating TPH genes and SB, the evidence is not entirely consistent. Therefore, we performed a meta-analysis to gain a better understanding into this issue.
  
  
  METHODS
  The meta-analysis was conducted with 37 articles of genetic association studies of TPH-1 (A218C and A779C) and TPH2 (G-703 T, A-473 T and G19918A) genes. To analyze the association of these variants with SB we used the following models: allelic, additive, dominant and recessive. In addition, we performed a sub-group analysis by Caucasian and Asian populations using the same four models.
  
  
  RESULTS
  TPH-1 gene variants showed a positive significant association with SB, but only in the fixed effects models. With regard to TPH-2 gene variants we could not find an association with SB.
  
  
  CONCLUSIONS
  The study provides evidence that A218C/A779C TPH-1 variants may be a risk factor to manifest SB at the clinical level, which is in agreement with previously reported meta-analyses. With regard to G-703 T/A-473 T/G19918A TPH-2 variants, our up-to-date meta-analysis could not detect any significant association between those genetic variants and SB. However, these results should be interpreted with caution since further studies need to be undertaken using larger sample sizes in different ethnic populations to confirm our findings.
authors.forename: Thelma Beatriz
authors.initials: TB
authors.lastname: González-Castro
authors.forename: Isela
authors.initials: I
authors.lastname: Juárez-Rojop
authors.forename: María Lilia
authors.initials: ML
authors.lastname: López-Narváez
authors.affiliation: División Multidisciplinaria de Comalcalco, Universidad Juárez Autónoma de Tabasco, Ranchería Sur, Cuarta Sección, Comalcalco, Tabasco, C,P, 86650, México. alfonso_tovillaz@yahoo.com.mx.
authors.forename: Carlos Alfonso
authors.initials: CA
authors.lastname: Tovilla-Zárate
mesh_terms: D000483:Alleles; D006801:Humans; D011110:Polymorphism, Genetic; D012307:Risk Factors; D059020:Suicidal Ideation; D014365:Tryptophan Hydroxylase / Q000235:genetics*; D044465:White People / Q000235:genetics
chemical_list: C497467:TPH1 protein, human; C494784:TPH2 protein, human; D014365:Tryptophan Hydroxylase