Mothers who smoke during pregnancy are more likely to have children with conduct disorder (CD), according to a study published in the journal JAMA Psychiatry.

The study, carried out by researchers at the University of Leicester in the UK, analyzed the relationship between smoking during pregnancy and the risk of the child developing CD.

CD is a behavioral problem where a child can become highly aggressive, antisocial and defiant.

There are two types of the disorder:

  • Early onset CD occurs when a child shows symptoms of the disorder before the age of 10, and is often associated to ADHD (attention deficit hyperactivity disorder)
  • Adolescent-onset is the most common type of this disorder, when the child shows CD symptoms after the age of 10. This often occurs alongside ADHD.

Researchers compared three studies for this latest research. The Christchurch Health and Development Study (CHDS), which includes biological and adopted children; the Early Growth and Development Study (EGDS), an adoption-at-birth study; and the Cardiff IVF (In Vitro Fertilization) Study (C-IVF), an adoption-at-conception study within genetically related families and genetically unrelated families.

The researchers looked at the levels of smoking during pregnancy, which were measured by the average number of cigarettes pregnant mothers smoked each day. This varied across all three studies.

Results revealed that children had a higher risk of developing CD if their mothers smoked during pregnancy, compared with mothers who did not smoke. This was the finding in both the children who were reared by genetically related mothers and those reared by genetically unrelated mothers.

Additionally, mothers who smoked more than 10 cigarettes a day had an even higher risk of their child developing CD.

Darya Gaysina of the University of Leicester says:

Our findings suggest an association between pregnancy smoking and child conduct problems that is unlikely to be fully explained by postnatal environmental factors (for example, parenting practices) even when the postnatal passive genotype-environment correlation has been removed.

The causal explanation for the association between smoking in pregnancy and offspring conduct problems is not known but may include genetic factors and other prenatal environmental hazards, including smoking itself.”

The study authors conclude that further research is needed, looking particularly at psychopathologic conditions to fully understand the association between smoking during pregnancy and conduct disorder.

The authors add that this could have important implications for future intervention and prevention programs aimed at remediating child conduct problems.

Previous studies have suggested that smoking during pregnancy can lead to ADHD. Research from Cincinnati Children’s Hospital Medical Center revealed that a child is 2.5 times more likely to develop ADHD if their mother smoked during pregnancy.