Higher levels of lithium in household tap water used for drinking by pregnant mothers could affect an important molecular pathway involved in neurodevelopment and autism, increasing the chances of offsprings developing autism spectrum disorder, according to scientists.
In the future, they said, human activities such as growing use of lithium battery and disposal in landfills potentially causing groundwater contamination could step up lithium levels in water.
The scientists from University of California Los Angeles (UCLA) Health, US, also said that the results of their study, based on data from Denmark, need to be replicated in other populations and areas of the world.
They have published their results in the Journal of American Medical Association (JAMA) Pediatrics.
"Any drinking water contaminants that may affect the developing human brain deserve intense scrutiny," said lead study author Beate Ritz, professor of neurology, UCLA Health.
Owing to lithium's mood stabilising effects, lithium compounds have long been used in the treatment of depression and bipolar disorders.
However, there is debate about the safety of lithium intake by pregnant mothers, amidst increasing evidence of its association with a higher risk of miscarriage and cardiac anomalies or defects in newborns.
Ritz found experimental research that found that lithium, one of the several naturally occurring metals often found in water, could affect an important molecular pathway involved in neurodevelopment and autism.
This study built on previous findings from Denmark's high-quality medical registry data that ingestion of chronic and low-dose lithium from drinking can influence the occurrence of adult onset neuropsychiatric disorders, said Zeyan Liew, first author of the study and assistant professor at Yale University School of Public Health, US.
Working with Danish researchers, who analysed lithium levels in 151 public waterworks in Denmark and using a nationwide database of patients with psychiatric disorders, the researchers identified children who were born in 1997-2013. They then compared 12,799 diagnosed with autism against 63,681 children who did not have an autism diagnosis.
The researchers reported that the risk of an autism diagnosis varied directly with lithium levels.
Dividing the lithium levels into quartiles, or four parts with each having a quarter of the values, they found that the second and third quartiles were associated with a 24-26 per cent higher risk of autism.
In the highest quartile, the risk was found to be 46 per cent higher compared to the lowest quartile.
They further found the association to be slightly stronger for those living in urban areas compared to those living in smaller towns and rural areas.
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