A new study has found that children exposed to smoking in the first four years of life were more likely to exhibit symptoms of hyperactivity and conduct problems.
“There is a lot of emphasis on the dangers of smoking during pregnancy, but our findings indicate that children continue to be vulnerable to the adverse effects of nicotine exposure during the first several years of life,” said lead author Lisa Gatzke-Kopp, Ph.D., of Pennsylvania State University.
For the study, researchers examined the effects of nicotine on 1,096 children by measuring the levels of a metabolic byproduct of nicotine called cotinine in their saliva.
The children’s saliva was tested when they were 6, 15, 24, and 48 months, the researchers reported. They added that this provided a more accurate measure of exposure than could be estimated from the parents’ reports of how much they smoked.
The children were recruited for the Family Life Project, a study of child development in areas of rural poverty. Half were boys, the other half girls, while 44% were African American.
The researchers’ analysis showed a linear association between cotinine and children’s symptoms of hyperactivity and conduct problems. This association remained significant even after controlling for family poverty levels, parental education, parental history of ADHD, hostility, depression, caregiver IQ, and obstetric complications. Additionally, this association was unchanged when excluding mothers who smoked during pregnancy, the researchers reported.
The study’s findings are consistent with animal studies demonstrating the effect of environmental exposure to nicotine on ongoing brain development in regions related to hyperactivity and impulsivity, according to the researchers.
This highlights the importance of mitigating children’s exposure to environmental smoke, including sources that extend beyond the parents, they add.
The study was published in the Journal of Child Psychology and Psychiatry.