Maternal and paternal smoking during pregnancy and risk of ADHD symptoms in offspring: testing for intrauterine effects.
Maternal smoking during pregnancy is associated with attention deficit hyperactivity disorder (ADHD) in offspring. It is assumed by many that this association is causal. Others suggest that observed associations are due to unmeasured genetic factors or other confounding factors. The authors compared risks of maternal smoking during pregnancy with those of paternal smoking during pregnancy. With a causal intrauterine effect, no independent association should be observed between paternal smoking and offspring ADHD. If the association is due to confounding factors, risks of offspring ADHD should be of similar magnitudes regardless of which parent smokes. This hypothesis was tested in 8,324 children from a well-characterized United Kingdom prospective cohort study, the Avon Longitudinal Study of Parents and Children (data from 1991-2000). Associations between offspring ADHD and maternal and paternal smoking during pregnancy were compared using regression analyses. Offspring ADHD symptoms were associated with exposure to both maternal and paternal smoking during pregnancy (mothers: β = 0.25, 95% confidence interval: 0.18, 0.32; fathers: β = 0.21, 95% confidence interval: 0.15, 0.27). When paternal smoking was examined in the absence of maternal smoking, associations remained and did not appear to be due to passive smoking exposure in utero. These findings suggest that associations between maternal smoking during pregnancy and child ADHD may be due to genetic or household-level confounding rather than to causal intrauterine effects.
MRC Centre for Neuropsychiatric Genetics and Genomics, Department of Psychological Medicine and Neurology, School of Medicine, Cardiff University, United Kingdom. langleyk@cardiff.ac.uk
Kate
K
Langley
Jon
J
Heron
George Davey
GD
Smith
Anita
A
Thapar
D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000209:etiology*; D001724:Birth Weight; D002648:Child; D005220:Fathers / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects; D009035:Mothers / Q000706:statistics & numerical data*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects; D006113:United Kingdom / Q000453:epidemiology
D014028:Tobacco Smoke Pollution