Figure 2

Distribution of polygenic scores in a case–control data set. The Wellcome Trust Case Control Consortium (WTCCC) phase I data set (N = 16,179 individuals) consisted of two control groups—the 1958 British Birth Cohort (58BC) and common controls recruited from the UK Blood Services (NBS)—and six disease groups: Crohn disease (CD), bipolar disorder (BD), coronary heart disease (CHD), type 1 diabetes (T1D), type 2 diabetes (T2D), and rheumatoid arthritis (RA). We compared the multiplicative polygenic risk score (MPRS) distributions between cases and controls, except for the hypertension group because of the small number of risk alleles (see Table 1). For all phenotypes, no significant difference was found between 58BC and NBS, and the mean MPRS of case groups was significantly higher as compared with the two control groups (Tukey’s honestly significant difference P values < 0.001 for all case versus control groups).