Sample demographics are summarized in Table 1 (and detailed in Supplementary Table 1). There were significant difference across the three clinical groups in; the common cognitive measure of vocabulary (p = 0.0005) [driven by both the COS (p = 0.005), and the SIB group (p = 0.02) having reduced scores compared to HCs], and race distribution (p = 0.0005) [due to proportionally less people of European descent in COS and SIB groups relative to HCs]. Vocabulary score did vary significantly by Val158Met genotype. More extensive cognitive measure available within the HC group showed a statistically non-significant trend for step-wise reduction in performance IQ with increasing Val load (114/113/111 for 0/1/2 Val alleles, p = 0.3), which was not seen for full-scale (p = 0.96) or verbal (p = 0.48) IQ. The Val allele was significantly over-represented in the COS (p = 0.04), but not in the SIB (p = 0.5) group relative to the HC group.
