. 2019 Nov 16;26(1):e12849. doi: 10.1111/adb.12849

TABLE 2.

Results of the Mendelian randomization analyses using summary‐level data from liability to substance use to adult ADHD risk (diagnosis received after age 18) including IVW estimates and four sensitivity analyses: weighted median, weighted mode, MR‐Egger, and GSMR

Exposure	Outcome	n SNPs	IVW				Weighted Median				Weighted Mode				MR‐Egger				n SNPs ^a	GSMR
			β	OR	95% CI	P	β	OR	95% CI	P	β	OR	95% CI	P	β	OR	95% CI	P		β	OR	95% CI	P
Smoking initiation	ADHD	346	1.31	3.72	3.10 to 4.44	2.9e−51	1.18	3.26	2.59 to 4.14	5.0e−22	1.04	2.84	1.17 to 6.82	.021	1.00	2.72	1.48 to 5.00	.001	330	1.24	3.46	2.89 to 4.14	1.4e−44
Alcohol drinks/wk	ADHD	90	0.01	1.01	0.57 to 1.79	.975	0.01	1.01	0.44 to 2.34	.978	−0.17	0.84	0.29 to 2.44	.747	−0.46	0.63	0.19 to 2.10	.444	80	1.08	2.95	1.67 to 5.21	.788
Alcohol problems	ADHD	7	0.59	1.81	0.14 to 24.05	.655	0.52	1.68	0.07 to 41.68	.752	0.78	2.18	0.03 to 165.67	.736	n.a.	n.a.	n.a.	n.a.	7	n.a.	n.a.	n.a.	n.a.
Alcoholdependence	ADHD	9	−0.23	0.80	0.53 to 1.20	.283	−0.13	0.88	0.52 to 1.49	.633	−0.69	0.50	0.21 to 1.21	.162	n.a.	n.a.	n.a.	n.a.	9	n.a.	n.a.	n.a.	n.a.
Cannabis initiation	ADHD	5	0.38	1.46	0.93 to 2.29	.103	0.48	1.62	1.01 to 2.59	.044	0.57	1.77	0.98 to3.19	.132	n.a.	n.a.	n.a.	n.a.	5	n.a.	n.a.	n.a.	n.a.
Coffee/d	ADHD	4	−0.01	0.99	0.66 to 1.49	.969	−0.01	0.99	0.73 to 1.35	.923	0.01	1.01	0.70 to1.46	.951	n.a.	n.a.	n.a.	n.a.	4	n.a.	n.a.	n.a.	n.a.

Note. The dichotomous variable smoking initiation was rescaled in the original GWAS such that its unit is a standard deviation increase in prevalence. ¹⁷ The ORs in this table reflect the change in ADHD diagnosis odds for a one‐unit increase in the exposure variable in the case of continuous exposure variables and the change in ADHD diagnosis odds per 2.72‐fold increase in the prevalence of the exposure variable for binary exposure variables (due to the log odds nature of the binary exposure GWAS data). For MR‐Egger, when I ² was 0.6‐0.9, a SIMEX correction was applied, while estimates were not reported at all when I ² was <0.6.

ADHD, attention‐deficit hyperactivity disorder; GSMR, generalized summary‐level‐data based Mendelian randomization; GWAS, genome‐wide association studies; n SNPs, number of SNPs included in the genetic instrument; n.a., the number of SNPs available for the analysis was too low, or, in the case of MR‐Egger, I ² was <0.6; SE, standard error of the beta; SIMEX, simulation extrapolation.

^{^a}

Number of SNPs left after the HEIDI filtering step, which is part of GSMR.