LDSC and GCTA were used to estimate SNP-chip heritability (h2SNP). Using both methods, female heritability estimates (29% average of LDSC=0.36 s.e.=0.12, P=0.003 and GCTA=0.21, s.e.=0.09, P=0.019) were comparable to those for other psychiatric disorders (see Figure 3). In contrast, in males, the point estimate was not significantly different from zero and was lower than previously reported estimates for major psychiatric disorders38 (7% average of LDSC=0.05, s.e.=0.13, P=0.69 and GCTA=0.08, s.e.=0.10, P=0.43). Analyzing males and females together—as has been done in published reports—the point estimate was 15% (average of LDSC=0.18, s.e.=0.06, P=0.003 and GCTA=0.12, s.e.=0.05, P=0.016). Partitioned heritability estimation39 will be conducted on future releases of PGC-PTSD data when the z-score for overall heritability is higher. The current z-score is 3.0, and a z-score of 7 was deemed adequate for partitioned heritability analysis in the primary publication.39
