Kids with stressed moms more prone to asthma
By Julie Steenhuysen
CHICAGO (Reuters) - Children whose mothers are stressed are at higher risk for asthma, Canadian researchers said on Tuesday.
They said persistent distress such as a mother's depression or anxiety can increase the risk that her child will develop asthma by an average of 25 percent, even after accounting for known environmental triggers.
"It is increasingly clear that traditional environmental risk factors do not fully explain the origins of asthma," said Anita Kozyrskyj of the University of Manitoba in Canada.
Kozyrskyj's team analyzed the medical records of nearly 14,000 children born in Manitoba in 1995 who were continuously registered with Manitoba Health Services until 2003.
They checked to see whether the children had asthma at age 7 by analyzing doctor visits, hospitalizations and medications in the year of their 7th birthday.
They cross-checked this with the mother's medical records, including doctor visits, hospitalizations and medication for depression and anxiety. And they ranked the mother's distress by the duration of treatment: no distress, postpartum distress only, short-term distress and long-term distress.
"We found that maternal distress which persists beyond the postpartum period is associated with an increased risk of asthma at school-age," Kozyrskyj, whose study appears in the American Journal of Respiratory and Critical Care Medicine, said in a statement.
This effect persisted even after factoring in income, gender, number of siblings, heredity and whether the child lived in an urban or rural setting.
The risk appeared to intensify for children in high-income households or who had more than one sibling.
While the reason these children are at higher risk is not clear, Kozyrskyj said it may be that mothers who are distressed are less likely to breast-feed and more likely to smoke.
"Depressed mothers are also less likely to interact with their infants," Kozyrskyj said in an e-mail. "Animal studies tell us that decreased attentiveness from the mother affects the infant's stress and immune response, but we are a ways from knowing whether this is true in humans."
Kozyrskyj said the study was unique because it characterized the effects of persistent stress on children of normal risk for asthma over a period of several years.
But she cautioned that stress is one of several risk factors for childhood asthma, which include genetics and environmental factors, such as maternal smoking.
More than 300 million people worldwide suffer from asthma, 22 million in the United States. Symptoms include wheezing, shortness of breath, coughing and chest tightness.
(Editing by Maggie Fox)