Children born to women who smoke cigarettes during pregnancy, especially when mothers are heavy smokers, are at an increased risk for attention-deficit/hyperactivity disorder (ADHD), a new review of medical studies confirms.
Mothers who smoked during pregnancy had an overall 60 per cent higher risk of having a child with ADHD compared to women who didn’t smoke. For mothers who smoked fewer than 10 cigarettes per day, the risk of having a child who developed ADHD was 54 per cent higher than for nonsmoking mothers. For mothers who were heavier smokers, the risk was 75 per cent higher than for nonsmokers.
An increased risk of ADHD for children of women who smoke while pregnant has been reported before. What’s new here, the authors say, is that the data have been pooled from studies in multiple countries and time periods, and also that as the daily tally of cigarettes went up, the risk of ADHD went up.
The findings “lend greater strength and credibility and statistical power to previous studies that likewise show that pregnant women who smoke have a greater likelihood of having a child with ADHD,” said Dr Andrew Adesman, chief, developmental and behavioural paediatrics, Steven and Alexandra Cohen Children’s Medical centre of New York in New Hyde Park.
Adesman, who was not involved in the research, told Reuters Health by phone that the study “has to be taken seriously. Women who smoke during pregnancy have one more reason to stop.”
Eleven per cent of US children ages 4 to 17, or 6.4 million children, have been diagnosed with ADHD based on parent reports, according to the centres for Disease Control and Prevention. ADHD can affect attention, hyperactivity and self-control, causing difficulty in school and socially.
As reported in paediatrics, Dr Dezhi Mu and colleagues at West China Second University Hospital in Chengdu, Sichuan, China, analysed 20 studies published between 1998 and 2017 that looked at the potential role of smoking during pregnancy and the risk of ADHD in offspring. Altogether, the studies involved nearly 3 million people in Europe, Brazil, Japan, Australia and the US.
The team found lower risks for ADHD in children of mothers who smoked in the US and Europe, where more smokers stop smoking when they get pregnant.
Data from seven studies showed that while mothers’ smoking had a greater effect than fathers’ smoking on ADHD risk, there was still a 20 per cent higher risk of ADHD in children born to fathers who smoked.