Scientists have known for a while that what happens during the foetal and early stages of a child’s life can have an impact on their later health.
Now, according to a news report, a long-term study of more than 3 000 children in the Avon Longitudinal Study of Parents and Children (ALSPAC) has shown that anxiety experienced during pregnancy has a link with hyperactivity later in life. The link between this factor and other ADHD symptoms, is however, still unclear.
Inattention not linked
ALSPAC, a project based in Bristol UK, monitored physical anxiety symptoms in 8 727 mothers between early pregnancy and her child reaching the age of five. The researchers classified these mothers as having low, medium or high anxiety levels and checked the performance of their children in attention tests once the children reached the age of eight. There was no difference in their attention span, no matter how high the anxiety level of the mother was.
However, when a larger group of children were tested at the age of 16, it was clear that there was a difference in hyperactivity symptoms depending on the mother’s anxiety level.
Dr Blanca Bolea, study leader, said the following: "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. 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. Around 28% of the women we tested showed medium or high anxiety. We controlled for hyperactivity in 3 199 children in total, and found that 224 children showed signs of hyperactivity, with the rate of hyperactivity more than double if the mother had suffered from medium or high anxiety."
A controversial illness
It's important to note that this study is only an association and we can’t say with certainty that it’s only anxiety during pregnancy that will cause hyperactivity in later life. There are a lot of other genetic, biological or environmental factors that need to be taken into account.
According to the press release explaining the study, it could be a 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."
Commenting, Professor Andreas Reif (University Hospital, Frankfurt) said:
"This is a very interesting study, especially given the longitudinal and transgenerational character and its large sample size. As with all studies of this design, one however must be cautious not to mix association with causation. As we know that ADHD and anxious traits are correlated on the genetic level, the finding could well be reflective of shared genetic influences. However, it is also important to stress that this study is not on anxiety disorders or ADHD, but rather on traits related to these disorders. For sure these data, however, further add to the emerging picture that ADHD / hyperactivity, anxiety and bipolar disorder are linked."
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