A new study adds to the scientific data behind the link to mothers who smoke during pregnancy and the increased risk of attention deficit hyperactivity disorder (ADHD) in their children. Published in the July 21 journal Pediatrics, the study also looked at the effects of using nicotine replacement products during pregnancy.
Researchers led by Jin Liang Zhu, PhD, an assistant professor of epidemiology at Aarhus University in Denmark, examined the medical records of 84,803 children born in Denmark to mothers who were recruited to be part of the study from 1996 to 2002. The mothers of the children in the study participated in four telephone interviews, answering questions about their smoking habits and that of their partner.
When the children were 7 years of age, the parents completed a behavior questionnaire about their child’s health, development and behavior. In addition to their responses, the research team had access to national registries in which children had been diagnosed with ADHD.
The investigators found that overall, a little more than 2,000 children in the study had been diagnosed with ADHD or had received ADHD medications. Among that group, children born to a mother who smoked were 1.6 times more likely to have ADHD than children born to a non-smoking mom. If the father also smoked, the risk increased to 1.8 times more than children of non-smoking parents.
As for nicotine replacement products such as patches and gum, the researchers saw a slightly higher risk of ADHD among mothers who used these products. However, because this group was small – only 29 mothers of children with ADHD had used the products during pregnancy – the study suggests but does not prove that nicotine itself, and not just tobacco, may be a hazard during pregnancy.
“We’ve been lulled into a false sense of security, thinking that if we can just get mothers to stop smoking and onto nicotine replacement, it will protect against any kind of fetal damage in the developing child. This is a stark injection of reality about how that may not be the case,” Timothy Wilens, MD, director of the Center for Addiction Medicine and acting chief of child psychiatry at Massachusetts General Hospital in Boston, told HealthDay.
The study authors acknowledge that other factors could be behind the link between smoking during pregnancy and ADHD. The disorder tends to run in families and families with ADHD are more likely to smoke, they wrote. This raises the possibility that the association may not be tied directly to the mother’s smoking, but could be the result of genetic and environmental influences.
Still, healthcare experts caution mothers to stop smoking before conceiving.
“If at all possible, try not to smoke when conceiving,” said Wilens, who was not involved in the study. “If you think you’ve conceived and you’re smoking, it’s best to come off cigarettes as quickly as possible. If you need to use nicotine replacement therapy, use it for as short a time as possible,” he advised.