Psoriasis cases were diagnosed by a dermatologist. Controls were at least 18 years of age and unaffected with psoriasis. All study participants were of self-reported European Caucasian ancestry. Cases and control individuals were recruited at five different locations - Michigan and Utah in the United States, Toronto and Newfoundland in Canada, and in Sweden.

Samples with > 2% missing genotypes on the Affymetrix Biobank Plus array, an absolute value of the F inbreeding coefficient > 0.03, significant non-Caucasian admixture by principal components analysis, or that were duplicates of or highly related to (Plink Pi_hat > 0.25) individuals within this dataset or with the other seven datasets of Tsoi et al. (2017) were removed before analysis. After quality control, 7,891 individuals from the Affymetrix Biobank Plus dataset (3,863 cases and 4,028 controls) were used for the meta-analysis of Tsoi et al (2017). However, the dataset deposited here (5,942 cases and 5,732 controls) represents application of all quality control filters except the removal of samples that were duplicates or relative pairs with individuals of the other seven datasets.