Polygenic risk scores for schizophrenia showed positive associations for ever vs. never use of cannabis across all p-value thresholds, with the strongest association for those SNPs with p-values below 0.01 in the original schizophrenia GWAS (see Figure 1, R2=0.47%, p=2.6×10−4). Significant associations were also seen in the analysis of quantity of cannabis use for 9 of the 10 SNP cut-offs, with the top association seen for those SNPs with p≤0.05 for schizophrenia (R2=0.85%, p=0.003). No association was seen with age at initiation of use, though the association with quantity of use remained significant when number of years of usage was accounted for (results not shown).
