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Original Article
April 2010

Association of Genetic Variants in the Neurotrophic Receptor–Encoding Gene NTRK2 and a Lifetime History of Suicide Attempts in Depressed Patients

Author Affiliations

Author Affiliations: Max Planck Institute of Psychiatry, Munich, Germany (Drs Kohli, Salyakina, Pfennig, Lucae, Horstmann, Menke, Kloiber, Hennings, Uhr, Müller-Myhsok, Holsboer, and Binder); and Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia (Drs Bradley and Ressler). Drs Kohli and Salyakina are now with the John P. Hussman Institute for Human Genomics, Miami, Florida. Dr Pfennig is now with the Department of Psychiatry and Psychotherapy, University Hospital Carl Gustav Carus, Technical University of Dresden, Dresden, Germany.

Arch Gen Psychiatry. 2010;67(4):348-359. doi:10.1001/archgenpsychiatry.2009.201
Abstract

Context  A consistent body of evidence supports a role of reduced neurotrophic signaling in the pathophysiology of major depressive disorder (MDD) and suicidal behavior. Especially in suicide victims, lower postmortem brain messenger RNA and protein levels of neurotrophins and their receptors have been reported.

Objective  To determine whether the brain-derived neurotrophic factor (BDNF) gene or its high-affinity receptor gene, receptor tyrosine kinase 2 (NTRK2), confer risk for suicide attempt (SA) and MDD by investigating common genetic variants in these loci.

Design  Eighty-three tagging single-nucleotide polymorphisms (SNPs) covering the genetic variability of these loci in European populations were assessed in a case-control association design.

Setting  Inpatients and screened control subjects.

Participants  The discovery sample consisted of 394 depressed patients, of whom 113 had SA, and 366 matched healthy control subjects. The replication studies comprised 744 German patients with MDD and 921 African American nonpsychiatric clinic patients, of whom 152 and 119 were positive for SA, respectively.

Interventions  Blood or saliva samples were collected from each participant for DNA extraction and genotyping.

Main Outcome Measures  Associations of SNPs in BDNF and NTRK2 with SA and MDD.

Results  Independent SNPs within NTRK2 were associated with SA among depressed patients of the discovery sample that could be confirmed in both the German and African American replication samples. Multilocus interaction analysis revealed that single SNP associations within this locus contribute to the risk of SA in a multiplicative and interactive fashion (P = 4.7 × 10−7 for a 3-SNP model in the combined German sample). The effect size was 4.5 (95% confidence interval, 2.1-9.8) when patients carrying risk genotypes in all 3 markers were compared with those without any of the 3 risk genotypes.

Conclusions  Our results suggest that a combination of several independent risk alleles within the NTRK2 locus is associated with SA in depressed patients, further supporting a role of neurotrophins in the pathophysiology of suicide.Published online February 1, 2010 (doi:10.1001/archgenpsychiatry.2009.201).

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