A University of Illinois at Chicago study reveals a link between smoking during pregnancy and very early-childhood behavior problems.
The research, published in the July/August issue of the journal Child Development, found that 2-year-olds regularly exposed to cigarette smoke in utero were nearly 12 times more likely to show clinical levels of behavior problems compared to toddlers who were not exposed.
"The ability to identify these disruptive behavior patterns in exposed children, even at this young age, is very striking," said Lauren Wakschlag, associate professor of psychiatry at the UIC College of Medicine's Institute for Juvenile Research and lead author of the study.
Researchers evaluated 93 children between their first and second birthdays. Forty-four children were exposed to cigarette smoke before birth, and among those exposed, nearly half of their mothers reported smoking more than half-a-pack a day.
The behaviors of exposed and non-exposed toddlers were compared to determine if early signs of disruptive behavior were evident in young children.
According to Wakschlag, toddlers prenatally exposed to cigarette smoke showed markedly different behavior patterns. Although many toddlers exhibit mild behavioral problems during this period -- known as the "terrible twos" -- the behavior problems of exposed toddlers significantly increased between 18 and 24 months of age compared to the milder, more stable patterns of non-exposed toddlers.
Wakschlag and her colleagues had previously reported links between prenatal smoking and antisocial behavior in older youth. Discovering that these patterns are evident as early as the first years of life has important implications for understanding the origins of psychiatric disorder.
"These findings suggest that for some children the roots of problem behavior may occur before they are born," she noted.
Disruptive behavior is multifaceted, according to Wakschlag, and includes aggression, irritability, rule-breaking and poor social skills.
To test which aspects of behavior are problematic for exposed children, the researchers also observed the toddlers' behavior in the laboratory. They found that exposed toddlers were more defiant, aggressive and had poorer social skills, but were not more irritable. This is important because different components of disruptive behavior reflect functioning within different areas of the brain.
While the study highlights increasing evidence of long-term problems associated with smoking during pregnancy, Wakschlag cautions that it does not prove smoking during pregnancy causes behavior problems.
"This study is another piece to this complex puzzle," said Wakschlag. "It moves us one step closer to figuring out whether smoking during pregnancy plays a causal role in the development of behavior problems. By pinpointing which behaviors are involved, it sets the stage for the next set of studies, which can more precisely characterize the relevant behaviors and their associated brain regions in exposed children."
Wakschlag and colleagues are currently conducting a follow-up study, funded by the National Institute of Drug Abuse, of behavioral patterns in prenatally exposed teenagers and how prenatal smoking may interact with genetic risk to contribute to problem behaviors.
"By the time parents seek help for children's disruptive behavior problems, these problems have often caused significant pain and suffering to the children, their families and society at large. Whether or not smoking during pregnancy causes behavior problems, this study highlights the importance of early identification and prevention.
"If we can detect problem patterns even at this young age," she said, "we should use this as an opportunity to help children get back on track."