Scientists have identified a link between lithium levels in Denmark’s water supply and an increased likelihood that children will later be diagnosed with autism.
Although the study of 52,706 children is not enough to prove that lithium directly causes autism, this possibility deserves further investigation.
A natural element and commonly used drug to treat mood disorders, lithium has been linked to miscarriages and heart defects in newborn babies. This is the first time an association has been made with Autism Spectrum Disorders (ASD).
“In this case-control study based on the Danish national population, the study team found that maternal exposure to higher levels of residential lithium in drinking water during pregnancy was associated with a moderate increase of ASD risk in offspring,” the researchers write in their published paper.
“The results remained robust after adjusting for several maternal neighborhood socioeconomic factors and air pollution exposures.”
Lithium typically ends up in drinking water through the weathering of underground minerals. Compared to other countries, metal levels in Denmark’s drinking water are moderate to low.
The researchers used patient databases and vital statistics information to identify children born between 2000 and 2013 with or without an autism spectrum disorder diagnosis, mapped to 151 different public aqueducts (representing the water supply of half of the country’s population).
Lithium concentrations in water were divided into four equal parts, with prenatal lithium exposure determined for each quartile. Levels in the second and third quartiles were associated with a 24-26% higher risk of autism diagnosis compared to the lowest quartile. In the highest quartile, this level of risk was 46% higher.
Of the 8,842 study participants with an autism diagnosis, 2,850 came from areas where lithium levels in drinking water were in the highest quartile, compared with 1,718 in the lowest quartile.
A similar relationship was discovered when researchers looked at individual autism subtypes. The link between lithium and autism was also slightly stronger for people living in urban areas compared to rural areas and small towns. The team added controls for certain socio-economic factors and air pollution.
“In the future, anthropogenic sources of lithium in water may become more prevalent due to the use and disposal of lithium batteries in landfills with potential for groundwater contamination,” says the neurologist. and epidemiologist Beate Ritz of the University of California, Los Angeles.
Lithium is known to be able to cross the placenta and the fetal blood-brain barrier, and research has already been done on the possibility that it may affect certain signals and pathways in the developing brain.
It’s a complicated picture, however: Lithium is also widely used as a mood balancer to treat people with bipolar disorder and depression. Higher levels of lithium in drinking water have also been linked to lower suicide rates, prompting arguments that the element may be artificially added to the water supply.
Further research will be needed to elucidate this relationship in order to overcome the limitations of the study. In the future, researchers could include water consumption, for example, rather than using the local drinking water source as a means of estimating exposure.
“Any drinking water contaminant that could affect human brain development deserves careful consideration,” says Ritz.
“The results of our study are based on high-quality Danish data but need to be replicated in other populations and regions of the world.”
The research has been published in JAMA Pediatrics.