Table 4.

Mediation of the effect of prenatal alcohol exposure on WISC-IV IQ^a by regional cortical thickness (N = 78)

Mediator	β1	β2	tb
Occipitotemporal
AA/day	−0.32**	−0.22†	−2.35**
AA/occasion	−0.21†	−0.07	−4.75***
Drinking days/week	−0.32**	−0.24*	−2.48**
Parietal
AA/day	−0.32**	−0.27*	−1.00
AA/occasion	−0.21†	−0.13	−1.38†
Drinking days/week	−0.32**	−0.26*	−1.20

β₁, standardized regression coefficient for alcohol in the regression of IQ on alcohol during pregnancy before controlling for mediator.

β₂, standardized coefficient for alcohol in the regression of IQ on alcohol during pregnancy after controlling for mediator.

^aWechsler Intelligence Scale for Children—Fourth Edition.

^bTests the significance of the change in the magnitude of the effect of the alcohol measure on IQ after the mediator has been entered into the model, using the difference in coefficients method (Clogg et al. 1992).

^†P < 0.10, *P < 0.05, **P < 0.01.