Estimate (b) | s.e. | P-value | 95% CI (lower) | 95% CI (upper) | |
---|---|---|---|---|---|

Low v. normal birth weight
| |||||

Model without mediator | |||||

Intercept | −1.18 | 0.01 | <0.001 | −1.20 | −1.16 |

Low birth weight → MDD (Path c) | 0.11 | 0.03 | <0.001 | 0.05 | 0.17 |

Model with mediator | |||||

Intercept | −2.17 | 0.02 | <0.001 | −2.21 | −2.14 |

Low birth weight → neuroticism (Path a) | 0.25 | 0.04 | <0.001 | 0.16 | 0.33 |

Neuroticism → MDD (Path b) | 0.22 | 0.00 | <0.001 | 0.22 | 0.23 |

Low birth weight → MDD (Path c’) | 0.07 | 0.03 | 0.040 | 0.00 | 0.13 |

Indirect effect (Paths a * b) | 0.05 | 0.01 | – | 0.04 | 0.07 |

Very low v. normal birth weight
| |||||

Model without mediator | |||||

Intercept | −1.18 | 0.01 | <0.001 | −1.20 | −1.16 |

Very low birth weight → MDD (path c) | 0.21 | 0.04 | <0.001 | 0.14 | 0.29 |

Model with mediator | |||||

Intercept | −2.18 | 0.02 | <0.001 | −2.12 | −2.14 |

Very low birth weight → neuroticism (Path a) | 0.26 | 0.06 | <0.001 | 0.15 | 0.38 |

Neuroticism → MDD (Path b) | 0.22 | 0.00 | <0.001 | 0.22 | 0.23 |

Very low birth weight → MDD (Path c’) | 0.18 | 0.04 | <0.001 | 0.10 | 0.26 |

Indirect effect (Paths a * b) | 0.06 | 0.01 | – | 0.03 | 0.09 |

Path

*a*: association between predictor and mediator (i.e., low/very low birth weight → neuroticism).Path

*b*: the mediator→ outcome association (neuroticism → MDD) adjusted for the predictor (birth weight).Path

*c*: the ‘total effect’ of the predictor → outcome (low/very low birth weight → MDD).Indirect effect: the product of Path

*a** Path*b*.Path

*c’*: the difference between Path*c*(‘total effect’) and the indirect effect (Path*a** b).^{11,23}