Table 6 Raw mediation statistics
Estimate (b)s.e.P-value95% CI (lower)95% CI (upper)
Low v. normal birth weight
Model without mediator
 Intercept−1.180.01<0.001−1.20−1.16
  Low birth weight → MDD (Path c)0.110.03<0.0010.050.17
Model with mediator
 Intercept−2.170.02<0.001−2.21−2.14
 Low birth weight → neuroticism (Path a)0.250.04<0.0010.160.33
 Neuroticism → MDD (Path b)0.220.00<0.0010.220.23
 Low birth weight → MDD (Path c’)0.070.030.0400.000.13
 Indirect effect (Paths a * b)0.050.010.040.07
Very low v. normal birth weight
Model without mediator
 Intercept−1.180.01<0.001−1.20−1.16
  Very low birth weight → MDD (path c)0.210.04<0.0010.140.29
Model with mediator
 Intercept−2.180.02<0.001−2.12−2.14
 Very low birth weight → neuroticism (Path a)0.260.06<0.0010.150.38
 Neuroticism → MDD (Path b)0.220.00<0.0010.220.23
 Very low birth weight → MDD (Path c’)0.180.04<0.0010.100.26
 Indirect effect (Paths a * b)0.060.010.030.09
  • 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