Mother's Smoking May Raise ADHD Risk in Children
But researchers say more study on the causes of the disorder is needed
By Randy Dotinga
TUESDAY, Dec. 3, 2013 (HealthDay News) -- A new study from Australia sheds more light on what environmental factors might raise the risk for attention-deficit/hyperactivity disorder (ADHD).
"Compared with mothers whose children did not have ADHD, mothers of children with ADHD were more likely to be younger, single, smoked in pregnancy, had some complications of pregnancy and labor, and were more likely to have given birth slightly earlier," said study co-author Dr. Carol Bower, a senior principal research fellow with the Center for Child Health Research at the University of Western Australia. "It did not make any difference if the child was a girl or a boy."
The researchers did find that girls were less likely to have ADHD if their mothers had received the hormone oxytocin to speed up labor. Previous research had suggested its use during childbirth might actually increase the risk of ADHD.
The causes of ADHD remain unclear, although evidence suggests that genes play a major role, said Dr. Tanya Froehlich, an associate professor at Cincinnati Children's Hospital Medical Center.
"Many prior studies have found an association between ADHD and [tobacco and alcohol exposure in the womb], prematurity and complications of pregnancy and delivery," she said.
One thing is certain: Diagnoses of ADHD have become common in the United States. A survey released in November found that 10 percent of American children have been diagnosed with the condition, although the rapid increase in numbers seems to have leveled off.
ADHD is more prevalent in boys. Its symptoms include distractibility, inattention and a lack of focus.
In the new study, researchers examined the medical records of nearly 13,000 children and young adults who were born in Western Australia and took stimulant medications for ADHD between 2003 and 2007. Stimulant drugs such as Ritalin and Adderall are typically used to treat ADHD.
The researchers compared the subjects to more than 30,000 other children to see if there were any environmental differences.
Although factors such as a mother's younger age and smoking during pregnancy were linked to a higher risk of ADHD in children, "low birth weight, birth at greater than full term and breathing difficulties in the baby were not more common [in the ADHD group]," Bower said.