After decades of research, the puzzle surrounding why some children develop autism spectrum disorder (ASD) continues to shake off easy answers, as no one single factor seems to be responsible. Currently, most scientists agree that a combination of genetic and environmental influences lead to the condition.
Exposure during pregnancy or early childhood to heavy metals such as mercury and lead has been linked to autism for decades, and the infamous, now-disproven link between vaccines and ASD stems in part from a theory that a mercury-containing preservative in some vaccines acts as a neurotoxin. Yet beside for avoiding obviously dangerous levels of mercury, the medical community’s advice on the safety of exposure to low levels of mercury has been conflicting, thanks to the lack of solid evidence from large, prospective human studies.
This lack of consensus has been particularly challenging for pregnant women who enjoy a fish-heavy diet or desire to eat fish because they are rich sources of the omega fatty acids known to benefit fetal health.
Now, insights from a nearly 20-year-long ongoing study by the University of Bristol appear to (finally) put the issue to rest. After analyzing data from more than 4,000 pregnancies, a team of authors found no association between the levels of mercury in the mother’s bloodstream and the child’s later diagnosis or absence of either ASD or individual autistic traits up to age 11.
"Our findings further endorse the safety of eating fish during pregnancy,” stated Professor Jean Golding, lead author of the investigation published in Molecular Autism. “Importantly we've found no evidence at all to support claims that mercury is involved in the development of autism or autistic traits.”