WASHINGTON – Two-year-olds whose mothers smoke regularly during pregnancy are significantly more likely to exhibit clinically disruptive behavior than are children of nonsmoking mothers, according to a review presented at a conference on tobacco control sponsored by the American Cancer Society.
“What we found was that nicotine exposure was linked to aggressive behavior, defiance, and lower social skills,” said Lauren S. Wakschlag, Ph.D., of the University of Illinois, Chicago.
“We still don't know that there is a causal link,” she said. “But the evidence that nicotine-exposed children are more likely to have behavior problems is there, and it is very consistent.”
To the researchers' surprise, nicotine exposure was not associated with emotional dysregulation–for reasons that remain unclear.
Ninety-three children were involved in the study. Overall, the 44 children exposed to nicotine in the womb were more defiant, more aggressive, and less social, compared with the 49 children who were not exposed–even after controlling for multiple variables.
The mothers were primarily non-Hispanic white and working class, which reflects the demographics of the typical pregnant smoker in the United States. Mothers of the nicotine-exposed children reported smoking consistently during at least two trimesters of their pregnancies, and 47% of them smoked more than half a pack (about 15 cigarettes) daily.
The children were assessed at 12, 18, and 24 months of age using maternal reports on the Infant-Toddler Social Emotional Assessment test. The 24-item ITSEA provides a clinical measurement of behavior in children as young as 1 year and rates traits such as peer aggression on a three-point scale. The children also were observed during a 20-minute interaction with their mothers in a laboratory setting.
Overall, nicotine-exposed children were almost 12 times as likely to have clinically significant behavior problems; 14 of 16 children with ITSEA scores in the clinical range were in the nicotine-exposed group, Dr. Wakschlag noted.
Mild behavior problems are common in toddlers, but the behavior of the nicotine-exposed toddlers was worse than that of the unexposed toddlers at the start of the study. In addition, the differences between the groups were significant by age 24 months, and the nicotine-exposed toddlers' behavior significantly worsened between ages 18 months and 24 months–the age at which some problem behaviors typically associated with the “terrible twos” start to decline, Dr. Wakschlag observed.
Identifying a pattern of behavior in toddlers who were prenatally exposed to nicotine could be useful in examining how other prenatal experiences affect behavior in early childhood.
“We have more work to do, but it is striking to see this level of coherence in the first year of life, and the specificity of the findings can help take the research further,” Dr. Wakschlag said. The next step, she said, is to link the behavior patterns of children who have been exposed to nicotine to neuroscientific investigations and to think about how nicotine exposure might interact with types of causal risks.
The data, which were published recently (Child Dev. 2006;77:893–906), support similar findings from another study. In the previous study, investigators found that maternal smoking during pregnancy was significantly associated with observed negativity in 52 toddlers whose mothers smoked throughout pregnancy, compared with 47 toddlers whose mothers did not smoke during pregnancy (Arch. Pediatr. Adolesc. Med. 2000;154:381–5).
ELSEVIER GLOBAL MEDICAL NEWS