Table 3. Polygenic Scoring.

P-value threshold	Major depressive disorder			Bipolar disorder			Schizophrenia
	NSNPs	PDiagnosis	PSeverity	NSNPs	PDiagnosis	PSeverity	NSNPs	PDiagnosis	PSeverity
0.05	103	0.908	0.907	176	0.226	0.077	140	0.981	0.631
0.1	172	0.339	0.559	282	0.429	0.197	244	0.831	0.623
0.2	309	0.067	0.127	446	0.360	0.119	381	0.555	0.285
0.3	423	0.093	0.109	611	0.479	0.091	514	0.675	0.485
0.4	530	0.086	0.073	736	0.401	0.041	621	0.663	0.383
0.5	632	0.067	0.044	849	0.397	0.045	715	0.433	0.257

Polygenic scores were derived for NHS participants using weights from PGC for major depressive disorder, bipolar disorder, and schizophrenia at varying p-value thresholds in the Psychiatric GWAS Consortium. For each disorder and p-value threshold, we report the number of SNPs used to derive the polygenic score (N_SNPs) and the p-value testing the association between the polygenic score and the PTSD phenotypes (P_Diagnosis, P_Severity) in NHS. The association between PTSD severity and the major depressive disorder and bipolar disorder polygenic scores becomes stronger at more liberal p-value thresholds. The most significant model for bipolar occurs at a p-value threshold of 0.4 (p=0.041, R2=0.3%).