In this research conversation, NICHD's Dr. James Griffin talks with grantee Dr. Leslie Leve on her study, which found a strong association between a mother's smoking during pregnancy and the chances that her child would have behavioral problems in school.
NICHD Research Conversations are audio interviews with NICHD scientists and grantees, on the latest NICHD-supported scientific findings. Listen to this Research Conversation at http://www.nichd.nih.gov/news/releases/Documents/NICHD_Research_Conversation_073013.mp3 (MP3 - 867 KB).
Mr. Robert Bock: Welcome to the National Institutes of Health. I'm Robert Bock, press officer for the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NICHD. Thank you for joining us for today's Research Conversation. Our host is Jim Griffin of the NICHD's Child Development and Behavior Branch. Today, Dr. Griffin will interview Dr. Leslie Leve, professor of Counseling, Psychology, and Human Services at the University of Oregon, and senior scientist of the Oregon Social Learning Center, in Eugene, about her research on the link between mothers smoking during pregnancy and the likelihood that their children will show signs of behavioral disorders during their early school years.
Dr. Jim Griffin: Thanks, Bob.
There's considerable evidence that when a woman smokes during pregnancy there's an increased risk that her child will grow up to exhibit emotional or behavioral problems, either as a preschooler or in their first years of elementary school. These problems include things like attention deficit hyperactivity disorder, otherwise known as ADHD, aggressive behaviors towards family members and playmates, destroying things like toys, books, and other household items, or breaking rules at school. Based on 2008 data from the Centers for Disease Control and Prevention, or CDC, approximately 13 percent of women reported smoking during the last three months of pregnancy, and a report from the Substance Abuse and Mental Health Services Administration found that, actually, pregnant white women had higher rates of smoking, at about 22 percent, compared to 14 percent among African-American women and 6.5 percent among Hispanic women.
Dr. Leslie Leve, our guest today, has published a study about the relationship between prenatal smoking and behavior problems in children in a recent issue of the Journal of the American Medical Association Psychiatry. Leslie, thank you for joining us today.
Now, first, can you tell us about your study and why it's an important step in understanding the relationship between smoking during pregnancy and child behavior problems?
Dr. Leslie Leve: Yes. Thank you, Jim. Our study was able to look at the relationship between smoking during pregnancy and child behavior problems in new ways because it included children from three separate studies, some of whom were raised by their biological mothers and some of whom were adopted at birth and raised by parents to whom they were not biologically related.
So, in this adoption study, which is called the Early Growth and Development Study, we interviewed over 300 adoptive mothers about the child's behavior problems and then we interviewed the child's birth mother to learn about her smoking habits during her pregnancy. The addition of this group of children who were adopted at birth enabled us to better separate the influences of events that happened before birth, such as smoking during pregnancy and genetic factors, from influences of the family environment that occur after a child is born.
So, for example, we know from previous studies of children who were raised by their biological parents that smoking during pregnancy is related to children's behavioral and emotional problems. If we can replicate this finding in our adoption at birth sample then we have stronger evidence that this association isn't just because of things happening in the family environment after birth but that the negative effects begin before a child is born.
And in our study, that is exactly what we found. Smoking during pregnancy was associated with children's behavioral problems both in the biological children as well as among the adopted children.
Dr. Griffin: OK. So, what can we say about the possible causes for the link you found? Do we know yet whether smoking itself somehow changes the children's brains to make it more likely for them to display behavior problems? Or could it be that the mothers who smoke have a genetic tendency towards poor impulse control, which they then passed on to their children?
Dr. Leve: Yeah, those are very important questions, Jim, and animal studies have shown that smoking during pregnancy does affect brain circuitry in nonhuman animals. In our study, we are not able to examine the children's brain function directly, but what we can do is separate out the effects that are due to circumstances and events that occur after birth from the events that occurred before birth. We know from other studies that the tendency to smoke is influenced by genes, and in our study the link between smoking during pregnancy and child behavior problems could be due to genes passed on from the biological mother to the child, or they could be due to changes in the child's brain development. And in either case, our study essentially allows us to more definitively conclude that what happens before birth can significantly affect children's behavior problems and that these effects are strong enough to be found across the three studies and across mother, father, and teacher ratings of children's behavior problems.
Dr. Griffin: OK. But what about how much a mother smokes? Do mothers who were heavier smokers have more impulsive children?
Dr. Leve: Yes. That is exactly what we found. So, we grouped families according to whether the child's biological mother had smoked at all during her pregnancy, whether she'd smoked one to nine cigarettes per day, or whether she smoked 10 or more cigarettes per day. And we found the associations between the amount of smoking so that parents and teachers were more likely to report conduct problems among children whose mother smoked 10 or more cigarettes a day than among those who smoked less than that or who didn't smoke at all, and therefore heavier smoking during pregnancy was really the most detrimental to children's adjustment.
Dr. Griffin: OK. In addition to the link between these behavioral problems and smoking during pregnancy, what other problems have been observed in the children of women who smoked during pregnancy?
Dr. Leve: Well, other studies have shown that smoking during pregnancy has been linked with complications very early in development, such as miscarriage, preterm birth, some birth defects, low birthweight, and even Sudden Infant Death Syndrome, SIDS. But we also know that smoking during pregnancy has been linked with problems for children later in development, such as aggression, antisocial behavior, and even their own later smoking behavior.
Dr. Griffin: OK. Thank you so much, Leslie, for telling us about this important work. That was Dr. Leslie Leve. And I want to let people know that, again, there's resources available if you're a woman who smokes and you're thinking about becoming pregnant or you already are pregnant and would like to quit. You can go to--all one word--SmokeFree.gov, that's SmokeFree.G-O-V, for more information on how to quit smoking.
And that concludes our Research Conversation for today. I'd like to thank Dr. Leve again for taking the time to speak with us and I'd like to thank our listeners for joining us.
About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's website at http://www.nichd.nih.gov/.