Table 2.

Reverse Mendelian randomization estimates for causal effects of genetically predicted IBD and its subtypes on SCZ.

Method	No. of SNPs	MR analysis			MR-Egger Intercept P
		OR	95% CI	P
IBD → SCZ
IVW	98	1.01	0.98 to 1.04	0.470	0.464
MR-Egger	98	0.99	0.92 to 1.06	0.690
Weighted Median	98	1.01	0.97 to 1.04	0.727
MR-PRESSOb	97	1.01	0.99 to 1.04	0.286
CD → SCZ
IVW	75	1.02	0.99 to 1.05	0.267	0.592
MR-Egger	75	0.99	0.92 to 1.08	0.923
Weighted Median	75	1.02	0.99 to 1.05	0.218
MR-PRESSOb	72	1.01	0.98 to 1.03	0.629
UC → SCZ
IVW	50	1.02	0.98 to 1.06	0.254	0.586
MR-Egger	50	1.05	0.94 to 1.17	0.375
Weighted Median	50	1.01	0.97 to 1.04	0.800
MR-PRESSOb	45	1.01	0.97 to 1.04	0.788

Note: MR Mendelian randomization, SCZ Schizophrenia, IBD Inflammatory bowel disease, CD Crohn’s disease, UC Ulcerative colitis, SNPs Single-nucleotide polymorphisms.

^aSNPs are selected at the genome-wide significant threshold of P < 5 × 10⁻⁸ with a linkage disequilibrium threshold of r² < .001 in a 10-Mb window.

^bOne outlier has been detected for MR estimate of IBD on SCZ, three outliers for CD on SCZ, five outliers for UC on SCZ.