The early effects of stress
When freezing rain fell on Quebec in January 1998, about 1.5 million people lost electricity, businesses closed for weeks and people in the Canadian province fell into various stages of anxiety and despair.
Six years later, Canadian researchers found some unlikely victims of the region’s worst ice storm in decades -- children who weren’t yet born. A new study of 53 women who were pregnant during the storm found a link between the women’s self-reported stress levels and how the children performed in language and intelligence tests at age 2. The children of those women who reported higher stress levels performed more poorly -- though still within “normal” ranges.
The Canadian research is one of two new studies that suggests a link between the emotional state of expectant mothers and the likelihood of behavior and learning difficulties in their children.
The two studies were relatively small, and researchers said the results would need to be confirmed in larger, more scientifically rigorous experiments.
In addition, it is difficult to isolate stress as the sole cause of any condition. Anxiety may also be the result of life events, such as divorce or job loss, said Suzanne King, a professor of psychiatry at Montreal’s Douglas Research Centre.
“And there’s no way to untangle that,” said King, who co-wrote the ice storm study, published July 7 in the online version of the journal Pediatric Research.
The studies are part of growing evidence that a woman’s emotional health during pregnancy, particularly in the second trimester, may be a risk factor for later behavioral problems in her children.
Most pregnant women aren’t exposed to something as stressful as a major natural disaster. But even minor stress could affect a developing child and might play a role in attention deficit hyperactivity disorder, or ADHD, a condition estimated to affect 4% to 12% of school-age children in the United States, according to a study published in the July/August issue of the journal Child Development.
In 1986, psychologists at Catholic University Leuven in Belgium followed 71 women through pregnancy, regularly checking their self-reported anxiety levels before and after their children’s births. Eight years later, researchers contacted the women to assess the children’s behavior. They asked the mothers, teachers, observers and the children themselves to rate their behavior.
The researchers found a correlation between the level of anxiety that women reported between weeks 12 and 22 of their pregnancy and behavioral problems in their children. Women who said they were very anxious during this period were more likely to have children who regularly had some ADHD symptoms, were anxious or had trouble controlling their behavior.
Between weeks 12 and 22, neurons are forming and traveling to different parts of the fetal brain. If something disturbs this development, it could affect the child’s behavior later, said Bea Van den Bergh, the lead author from Catholic University.
Whether ADHD occurs because of a mother’s worrying is not clear, said Dr. David Feinberg, a child psychiatrist at UCLA. It could be a combination of things, including genetics and maternal smoking.
“Of course, it is plausible that highly anxious mothers are carrying genes for ADHD,” the study said. If those mothers are also anxious during pregnancy, it’s possible the ADHD genes could be activated in their children.
Neither study measured levels of the stress hormone cortisol in the mother’s blood during pregnancy, which may be a more reliable measure of anxiety than a person’s self-assessment, the Belgian study said. Studies in monkeys have shown that stress can decrease the placenta’s ability to protect the fetus against cortisol, increasing the risk of brain impairment.
