Table 1. Variance explained (R ²) and P-values of the association of PSS (based on different P-value thresholds) and of PWM (based on the complete or partial SNP set) with total brain, white matter and gray matter volumes in the healthy target sample (N=122).

	No. SNPs	Total brain		White matter		Gray matter
		R2 change	P-value	R2 change	P-value	R2 change	P-value
PSS (polygenic SCZ risk score)
P<0.0001	106	−0.007	0.613	−0.008	0.740	−0.007	0.590
P<0.0005	311	−0.009	0.928	−0.010	0.903	−0.009	0.801
P<0.001	482	0.007	0.180	−0.009	0.776	0.023	0.054
P<0.005	1480	−0.006	0.559	−0.009	0.983	0.000	0.320
P<0.01	2528	−0.005	0.507	−0.006	0.558	−0.005	0.570
P<0.05	8555	−0.006	0.582	−0.007	0.613	−0.008	0.710
P<0.1	14 491	−0.009	0.819	−0.008	0.678	−0.009	0.999
P<0.2	24 870	−0.008	0.689	−0.009	0.856	−0.007	0.624
P<0.3	33 660	−0.007	0.635	−0.010	0.941	−0.005	0.489
P<0.4	41 398	−0.007	0.661	−0.007	0.941	−0.003	0.445
PWM (polygenic white matter score)
Complete SNP set	185	−0.008	0.719	−0.009	0.744	−0.001	0.333
Partial set	142	−0.002	0.391	−0.009	0.872	0.006	0.187

Abbreviations: SCZ, schizophrenia; SNP, single-nucleotide polymorphism. R² refers to R² adjusted for the number of predictors in the model.