Association of COMT and TPH-2 genes with DSM-5 based PTSD symptoms

- The higher heritability of PTSD symptoms (0.60) based on DSM-5 criteria compared to DSM-IV (0.41) suggests that DSM-5 based assessments may increase the prospects of finding genetic markers.
- Significant association between synonymous COMT SNP allele 4633C and DSM-5 based total PTSD and D category, but not C category severity scores. No genetic correlation between C and D categories
- The findings provide biological support for dividing DSM-IV category C symptoms into DSM-5 category C and D symptoms.
- COMT rs4633C and TPH-2 rs11178997T alleles jointly explained 7% of the variance in PTSD severity scores Carriers of these alleles may be at risk of PTSD.

BackgroundDopaminergic and serotonergic systems have been implicated in PTSD. The present study evaluated the association of four catechol-O-methyltransferase (COMT) gene loci, and the joint effect of COMT and tryptophan hydroxylase 2 (TPH2) genes on PTSD symptoms.MethodsSubjects included 200 Caucasian Armenian adults exposed to the 1988 Spitak earthquake from 12 multigenerational (3-5 generations) families. Instruments used included the UCLA PTSD Reaction Index based on DSM-5 criteria, and the Beck Depression Inventory.ResultsThe adjusted heritabilitiy of vulnerability to DSM-5 based PTSD symptoms was 0.60 (p<10−4). There was a significant association of the COMT allele rs4633C with total PTSD (p<0.03), and D category (p<0.04) (negative alterations in cognitions and mood) severity scores, but not with C category (avoidance) scores. There was no genetic correlation between C and D category severity scores. COMT allele rs4633C and the TPH-2 allele rs11178997T together accounted for 7% of the variance in PTSD severity scores (p<0.001). None of the COMT alleles were associated with depression.LimitationsThe ratings of earthquake exposure and prior trauma may have been subject to recall bias. The findings may not be generalizable to other ethnic/racial populations.ConclusionCOMT allele rs4633C may be causally related and/or is in linkage disequilibrium with gene(s) that are causally related to PTSD symptoms. Carriers of these COMT and the TPH-2 alleles may be at increased risk for PTSD. The findings provide biological support for dividing DSM-IV category C symptoms into DSM-5 categories C and D.