TABLE 3

The Association Between Maternal Smoking and Offspring ADHD Diagnoses Compared With the Associations With Three Negative Controls, Mutually Adjusted for Each Other

CrudeaAdjustedb
Hazard RatioP95% CIχ2 ValueP Value χ2 TestHazard RatioP95% CIχ2 ValueP Value χ2 Test
Maternal smoking 1.93<.0011.70–2.197.47.0061.39<.0011.22–1.592.64.10
Paternal smoking1.48<.0011.34–1.641.19.0011.07–1.33
Maternal smoking 2.16<.0011.90–2.4517.47<.0011.44<.0011.25–1.652.89.09
Grandmother’s smoking1.45<.0011.30–1.621.22<.0011.09–1.36
Maternal smoking Maternal smoking in previous pregnancies1.65<.0011.37–2.000.03.871.29.0081.07–1.560.06.81
1.70<.0011.43–2.021.34.0011.14–1.59
  • CI, confidence interval.

  • a Maternal smoking and the negative controls mutually adjusted for each other, but not adjusted for covariates.

  • b Maternal smoking and the negative controls mutually adjusted for each other and for the following covariates: maternal and paternal age, maternal and paternal education, maternal and paternal ADHD symptoms, maternal (prepregnancy) and paternal BMI, maternal alcohol consumption during pregnancy, parity, child’s birth year, and geographical region. χ2 values were obtained from testing 3 null hypotheses that the association between maternal smoking and offspring ADHD diagnoses was equal to each of the 3 other associations (Wald tests). Degrees of freedom = 1 in all tests.