Children of parents who both smoke during the pregnancy have an 83 percent higher risk of developing ADHD than children of two non-smokers. The mother’s smoking appears to be particularly important.
Furthermore, it is now possible to tie pregnant women's use of nicotine patches and nicotine chewing gum to an increased risk of the child developing ADHD. The risk corresponds to the risk found among the children of a mother who smokes.

This is the result of new research from Aarhus University on the basis of data from 84,803 Danish children born in the period 1996 to 2002. The results have been published in the journal Pediatrics.

"Our study does not, however, necessarily mean that it is of importance for the development of ADHD that the foetus is exposed to nicotine. It could also be due to the fact that the nicotine-dependent women pass a genetic predisposition for ADHD on to their children," says Professor Carsten Obel from Aarhus University.

In other words, it is not possible to conclude that smoking or nicotine is the cause of ADHD and the researchers have not clarified the causal link behind the disorder.

Higher birth weight than for smokers

The survey also points to the use of nicotine patches not having the same significance for birth weight as smoking: Mothers who stopped smoking and instead used nicotine patches etc. thus gave birth to children at the same level as non-smokers.

"So even though we cannot say anything conclusive about a causal relationship between nicotine and ADHD, my advice to smokers would be to try and quit tobacco and nicotine patches even before the pregnancy. But if this is not possible then it is better to use patches and nicotine chewing gum than it is to smoke because they apparently do not affect the child's birth weight," says Carsten Obel.

• Read the article in the journal Pediatrics.

 Facts:

• The study is based on interviews with mothers from the national birth cohort "Better Health for Mothers and Children." They were asked about their own and their partners smoking habits during pregnancy.
• Mothers were also asked about their consumption of nicotine patches, nicotine spray and nicotine chewing gum.
• The researchers have followed 84,803 children until 2011 with a focus on whether they were diagnosed or treated for ADHD. Around two percent were. 
• Children with ADHD were identified via the Danish Psychiatric Central Register, the Danish National Patient Register and the Register of Medicinal product Statistics.

Further information:

Professor, PhD Carsten Obel
Department of Public Health, Aarhus University
Tel.: +45 2942 8405
co@ph.au.dk