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. 2019 Jan 31;16(1):e1002739. doi: 10.1371/journal.pmed.1002739

Fig 1. Schematic representation of MR analyses.

Fig 1

(a) BMI SNPs were used as instrumental variables to investigate the causal effect of BMI upon psoriasis. (b) Psoriasis SNPs were used as instrumental variables to investigate the causal effect of genetic risk of psoriasis upon BMI. Arrows indicate MR assumption such that the instrumental variable is associated with the exposure—not associated with confounders—and only affects the outcome via the exposure. BMI, body mass index; MR, mendelian randomization; SNP, single-nucleotide polymorphism.