Children who are exposed to maternal anxiety in the womb and during the first few years of life are twice as likely to have symptoms of hyperactivity at age 16, according to a long-term study of more than 3,000 children.
Interestingly, the researchers found no significant link between maternal anxiety and other attention-deficit/hyperactivity disorder (ADHD) symptoms, such as inattention.
“This is the first time that a study has shown that anxiety is linked to a child’s hyperactivity in later life but that inattention is not linked,” said Dr. Blanca Bolea, who led the study when she was at the University of Bristol. She is now assistant professor at the University of Toronto in Canada.
“One interpretation is that some symptoms of ADHD are associated with the mother’s anxiety, but not all of them. More broadly, it shows that the stresses a mother experiences can show up in her child nearly a generation later; it is worth noting that all the mothers reported an increase in anxiety during pregnancy.”
For the study, the researchers evaluated data from the Avon Longitudinal Study of Parents and Children (ALSPAC), a long-term project based in Bristol U.K., which allows scientists to track how children’s health changes over time.
The study recorded reported levels of some physical symptoms of anxiety such as sweating, trembling, dizziness and insomnia in 8,727 mothers in the period between early pregnancy and her child up to age 5. Based on these self-reported symptoms, the researchers classified the mothers into three categories: low anxiety, medium anxiety, or high anxiety.
When the children reached 8 and a half years of age, they completed attention tests. The researchers found no attention differences between the children, no matter how anxious the mothers had been.
However, testing a larger group of 3,199 children at the age of 16 showed that there was a significant difference in hyperactivity symptoms, depending on how anxious the mother had been.
On average, children with moderate- or high-anxiety mothers were around twice as likely to show symptoms of hyperactivity at age 16, compared with children with low-anxiety mothers. This means that 11% of the children from “high anxiety” mothers, and 11% of children from “moderate anxiety” mothers showed symptoms of hyperactivity. Only 5% of children from ‘”low anxiety” mothers showed hyperactivity symptoms.
“This is an association, so we can’t 100% say that anxiety symptoms in pregnancy and early life causes later hyperactivity, other genetic, biological or environmental effects may be at play. However, this idea is supported by studies in animals,” said Bolea.
“We’re not sure why this might happen. It could be that the children are responding to perceived anxiety in the mother, or it could be that there is some biological effect which causes this, for example stress hormones in the placenta having an effect on a developing brain. ADHD is a controversial illness, and there doesn’t seem to be any single cause, though we know it can be hereditary. This work shows that maternal anxiety is one factor which is linked to ADHD, but we need some more research to confirm this and other causes.”
The research was presented at the European College of Neuropsychopharmacology (ECNP) Congress in Copenhagen.