The Psychiatric Genomics Consortium-Posttraumatic Stress Disorder group (PGC-
PTSD) combined genome-wide case–control molecular genetic data across 11
multiethnic studies to quantify PTSD heritability, to examine potential shared
genetic risk with schizophrenia, bipolar disorder, and major depressive
disorder and to identify risk loci for PTSD. Examining 20 730 individuals, we
report a molecular genetics-based heritability estimate (h2SNP) for European-
American females of 29% that is similar to h2SNP for schizophrenia and is
substantially higher than h2SNP in European-American males (estimate not
distinguishable from zero). We found strong evidence of overlapping genetic
risk between PTSD and schizophrenia along with more modest evidence of overlap
with bipolar and major depressive disorder. No single-nucleotide polymorphisms
(SNPs) exceeded genome-wide significance in the transethnic (overall) meta-
analysis and we do not replicate previously reported associations. Still, SNP-
level summary statistics made available here afford the best-available
molecular genetic index of PTSD—for both European- and African-American
individuals—and can be used in polygenic risk prediction and genetic
correlation studies of diverse phenotypes. Publication of summary statistics
for ∼10 000 African Americans contributes to the broader goal of increased
ancestral diversity in genomic data resources. In sum, the results demonstrate
genetic influences on the development of PTSD, identify shared genetic risk
between PTSD and other psychiatric disorders and highlight the importance of
multiethnic/racial samples. As has been the case with schizophrenia and other
complex genetic disorders, larger sample sizes are needed to identify specific
risk loci