March 8, 2007 — -- Smoking during pregnancy may have longer lasting effects on your child than you might think -- particularly on a child's long-term behavior.
Michigan State University researchers Dr. Joel Nigg and Dr. Naomi Breslau addressed these effects in a study published in this month's Journal of the American Academy of Child and Adolescent Psychiatry.
Nigg and Breslau followed just over 700 children from age 6 through age 17, randomly selected from two groups: those with normal birth weight and those with low birth weight (less than 5 lbs 8 oz).
Their main goal was to tease out the influences of low birth weight and maternal smoking -- singly and combined -- on the development of attention deficit hyperactivity disorder (ADHD), as well as two other specific behavioral disorders in children: Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD).
Most people are familiar with ADHD, a syndrome that is first recognized in early childhood and is characterized by the core symptoms of hyperactivity, impulsivity and inattention.
Less well-known is ODD. Children with this condition frequently show loss of temper, are argumentative with adults, and refuse to obey rules, deliberate annoyance of others, as well as spitefulness and vindictiveness.
CD, another lesser known disorder, is thought to be a progression of ODD in most cases, includes more severe behaviors. These include aggression toward animals and people, destruction of property, excessive lying, theft, and serious violation of rules.
Using a variety of accepted methods to diagnose behavioral disorders, these researchers found that a mother's smoking during pregnancy influences the development of ODD and, later, CD.
The effect of smoking was independent of birth weight, as well as other maternal factors such as the mother's education, urban vs. suburban residence, and alcohol or drug abuse by the mother.
Taken together, these findings mean that a clearer line than ever can be drawn implicating smoking as a primary cause of these behavioral disorders.
Smoking by mothers during pregnancy has long been recognized as a risk factor for low birth weight, premature birth, and a variety of infant and early childhood problems. However, late effects of maternal smoking into the teenage years have rarely been studied.
In addition, most of the work done in this area has focused on smoking, low birth weight and risk for ADHD. These studies have found conflicting results regarding maternal smoking -- some suggesting a risk of developing ADHD, and others failing to find such relationships.
While most studies have focused on either smoking or low birth weight separately, very few have studied specific behavioral disorders. Fewer still have followed children over long periods of time, highlighting the importance of this study.
In fact, up to a quarter to a third of children with ADHD will also have either ODD or CD. And while ADHD, ODD and CD show patterns of common genetic inheritance, twin studies have confirmed that environment plays an equally important role.
Hence, yet another reason for pregnant women to stop smoking.
These three behavioral disorders have important life-long implications. ADHD, for example, continues into adulthood in up to half of cases. People with this disorder have impaired educational attainment, and, although they are employed at the same rate as people without ADHD, they tend to achieve lower work status due to poorer performance at work.
Even in the absence of ODD or CD, children with ADHD also are at increased risk for developing substance abuse, as well as antisocial personality. They tend to have more injuries and more motor vehicle accidents.
Fortunately, a number of medications such as methyphenidate (Ritalin and Concerta), as well as psychological and educational support, can greatly enhance future academic, social and employment success.
Treatment for ODD and CD can be more challenging. Authorities feel that it should involve health care professionals as well as emotionally engaged parents. This can be difficult; because ODD and CD are at least partially hereditary, parents themselves may possess similar traits. This often worsens parental reactions to unwanted behaviors of the child and increases the likelihood of harsh punishments and angry interactions.
Nigg and Breslau conclude that although ADHD, ODD and CD exhibit some common hereditary factors, maternal smoking -- and, for ADHD, low birth weight -- are also very important contributors.
Women who are smokers should quit entirely throughout their pregnancy -- and, of course, remain smoke-free to enhance long-term health of their child and themselves.
There are a number of strategies to achieve this goal, some better than others.
Use of nicotine replacement is problematic. The American College of Obstetricians and Gynecologists suggests that nicotine should only be used as a second line method to quit smoking if behavioral change and counseling have not been effective, as, they note, "nicotine replacement exposes the fetus to a steady dose of nicotine, which may lead to neurotoxicity."
But other successful quit strategies for pregnant women, including behavioral modification and use of self-help groups and other support services, increase their children's chances of a healthy start in life.
Dr. John Spangler is director of tobacco control intervention programs and professor of family medicine at Wake Forest University School of Medicine.