. Author manuscript; available in PMC: 2020 Aug 1.

Published in final edited form as: Lancet Psychiatry. 2019 Nov 20;7(2):208–216. doi: 10.1016/S2215-0366(19)30293-7

Table 3. A rough guide to sample size requirements for MR studies.

An illustration of minimum sample sizes required for MR studies, taken from the online calculator available at http://cnsgenomics.com/shiny/mRnd/ ⁶⁹ Results shown are for a binary outcome, assuming 25% cases in study, 0.8 power and alpha 0.05.

Variance explained	Estimated Effect Size (OR)	Minimum Sample size

1%	1.01	42,069,473
	1.1	439,015
	1.5	20,408
	2	5,756

5%	1.01	8,413,895
	1.1	87,803
	1.5	4,082
	2	1,152