In these analyses, we calculated genetic risk scores for schizophrenia (supplementary Figure 1A) and tested whether the risk scores predicted FTND and CPD. The results were summarized in Table 1. Schizophrenia risk scores predicted FTND score and CPD at the thresholds of P ≤ 5 × 10−3, 5 × 10−2 and 5 × 10−1. The correlation coefficients at these thresholds were all positive, suggesting that a schizophrenia diagnosis was positively associated with cigarette smoking, consistent with the well-known comorbidity between schizophrenia and ND. However, schizophrenia risk scores explained only a very small fraction of the FTND and CPD traits.
