Table 2.
Two-sample MR analyses of the effect of schizophrenia and depression on smoking
| Exposure | Outcome | Method | N SNP | β (95% CI) | p value |
|---|---|---|---|---|---|
| Schizophrenia | Lifetime smoking | Inverse-variance weighted | 102 | 0.022 (0.005–0.038) | 0.009 |
| MR Egger (SIMEX) | – | – | – | ||
| Weighted median | 102 | 0.015 (0.004–0.026) | 0.009 | ||
| Weighted Mode | 102 | 0.016 (−0.014 to 0.045) | 0.31 | ||
| MR RAPS | 102 | 0.018 (0.003–0.032) | 0.015 | ||
| Depression | Lifetime smoking | Inverse-variance weighted | 34 | 0.091 (0.027–0.155) | 0.005 |
| MR Egger (SIMEX) | – | – | – | ||
| Weighted median | 34 | 0.100 (0.058–0.141) | 2.77 × 10−06 | ||
| Weighted mode | 34 | 0.109 (0.037–0.182) | 0.005 | ||
| MR RAPS | 34 | 0.078 (0.014–0.141) | 0.016 | ||
| Schizophrenia | Smoking initiation | Inverse-variance weighted | 107 | 0.010 (0.000–0.021) | 0.04 |
| MR Egger (SIMEX) | 107 | −0.030 (−0.093 to 0.033) | 0.35 | ||
| Weighted median | 107 | 0.003 (−0.006 to 0.012) | 0.53 | ||
| Weighted Mode | 107 | −0.008 (−0.033 to 0.017) | 0.54 | ||
| MR RAPS | 107 | 0.008 (−0.002 to 0.017) | 0.11 | ||
| Depression | Smoking initiation | Inverse-variance weighted | 34 | 0.083 (0.039–0.127) | 2.32 × 10−04 |
| MR Egger (SIMEX) | – | – | – | ||
| Weighted median | 34 | 0.077 (0.042–0.112) | 1.55 × 10−05 | ||
| Weighted mode | 34 | 0.062 (0.007–0.117) | 0.03 | ||
| MR RAPS | 34 | 0.077 (0. 037–0.117) | 1.64 × 10−04 |
SIMEX, simulation extrapolation, MR RAPS, robust adjusted profile score.
Note: Due to low regression dilution I2GX (see online Supplementary Table S3), MR Egger estimates could not be conducted apart from for the effect of schizophrenia on smoking initiation, where a weighted MR Egger SIMEX was conducted. Smoking initiation scores are given in βs by GSCAN calculated from the meta-analysed z-score statistic by assuming a prevalence for the binary trait (Liu et al., 2019).