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Parental smoking linked to ADHD risk in offspring

Prenatal exposure to smoking could increase the risk for attention-deficit/hyperactivity disorder in children, according to recent study findings published in Pediatrics.

Jin Liang Zhu, PhD, of the University of Aarhus in Denmark, and colleagues evaluated a cohort of 84,803 singleton births and their parents’ smoking habits to determine the association of parental smoking in pregnancy and ADHD. Children were followed up for 8-14 years.

Jin Liang Zhu

At follow-up, 2.4% of participants were diagnosed with ADHD or received an ADHD medication.

“Pregnant women should, with psychosocial support, be encouraged to quit smoking preferably without the use of nicotine replacement,” Zhu told Healio.com. “Although more studies are needed to determine to what extent the link between maternal tobacco smoking and offspring ADHD is causal, the consistent association should lead clinicians to awareness of possible ADHD symptoms in children born to smoking mothers.”

Parental smoking, overall, was linked to a higher risk for ADHD diagnosis or medication, but maternal smoking had a greater risk than paternal smoking. Participants with smoking mothers and nonsmoking fathers were at increased risk for ADHD compared with participants whose parents did not smoke (HR=1.63; 95% CI, 1.36-1.94). Similarly, participants with nonsmoking mothers but smoking fathers had a higher risk compared with participants with nonsmoking parents (HR=1.29; 95% CI, 1.14-1.47).
Participants also had a higher risk for ADHD if their mothers used nicotine replacement during pregnancy.

”As we saw that women using nicotine replacement, as well as quitters, had close to the same birthweight as nonsmokers, this is a good argument for preferring quitting as well as replacement for smoking,” study researcher Carsten Obel, MD, PhD, also of Aarhus University, told Healio.com. “Even though we are not sure if the nicotine link is causal or due to genetic confounding, the best advice in relation to ADHD at this point will probably be to try to stop smoking without the use of nicotine replacement and preferably before getting pregnant. If this is not possible, nicotine replacement is, based on the birthweight results, preferable in comparison with continuing to smoke.”

Carsten Obel

Obel added that more studies need to be conducted in order to determine if there is a causal link between maternal smoking and offspring ADHD.

“There is generally a need for collaboration between the professionals managing antenatal care to support the women in this situation, not only targeting smoking women but vulnerable women in general,” he said. “ADHD is often harder to detect in women and more attention on possible ADHD in the pregnant smoker may be an important area of focus in developing clinical practice.”

Jin Liang Zhu, PhD, can be reached at Section of Epidemiology, Department of Public Health, University of Aarhus, Bartholins Allé 2, DK-800 Aarhus C, Denmark; email: zj;@ph.au.dk.

Carsten Obel, MD, PhD, can be reached co@ph.au.dk.

Disclosure: The study was funded in part by the European Research Council and the Tryg Foundation. The researchers report no relevant financial disclosures.