Association study of trauma load and SLC6A4 promoter polymorphism in posttraumatic stress disorder: evidence from survivors of the Rwandan genocide.
OBJECTIVE
As exposure to different types of traumatic stressors increases, the occurrence of posttraumatic stress disorder (PTSD) increases. However, because some people exhibit either surprising resilience or high vulnerability, further influencing factors have been conjectured, such as gene-environment interactions. The SLC6A4 gene, which encodes serotonin transporter, has been identified as predisposing toward differential emotional processing between genotypes of its promoter polymorphism.


METHODS
We investigated 408 refugees from the Rwandan genocide and assessed lifetime exposure to traumatic events, PTSD (according to DSM-IV) status, and genotype of the SLC6A4 promoter polymorphism. The study was conducted from March 2006 to February 2007.


RESULTS
The prevalence of PTSD approached 100% when traumatic exposure reached extreme levels. However, persons homozygous for the short allele of the SLC6A4 promoter polymorphism showed no dose-response relationship but were at high risk for developing PTSD after very few traumatic events. This genotype influence vanished with increasing exposure to traumatic stressors.


CONCLUSIONS
We find evidence for a gene-environment interplay for PTSD and show that genetic influences lose importance when environmental factors cause an extremely high trauma burden to an individual. In the future, it may be important to determine whether the effectiveness of therapeutic interventions in PTSD is also modulated by the SLC6A4 genotype.
Kolassa
Iris-Tatjana
IT
Clinical Psychology and Neuropsychology and Zukunftskolleg, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany. Iris.Kolassa@uni-konstanz.de
Ertl
Verena
V
Eckart
Cindy
C
Glöckner
Franka
F
Kolassa
Stephan
S
Papassotiropoulos
Andreas
A
de Quervain
Dominique J-F
DJ
Elbert
Thomas
T
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D006708:Homicide / Q000523:psychology*; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic / Q000235:genetics*; D011569:Psychiatric Status Rating Scales; D012432:Rwanda; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D013313:Stress Disorders, Post-Traumatic / Q000235:genetics* / Q000523:psychology; D013315:Stress, Psychological / Q000235:genetics* / Q000523:psychology; D017741:Survivors / Q000523:psychology*; D055815:Young Adult
C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins