Study finds slightly higher risk of autism diagnosis in areas with more lithium in drinking water, but experts say more research is needed

CNN
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A new study found a moderately higher risk of autism spectrum disorder in children born to pregnant women exposed to tap water containing higher levels of lithium, but experts caution that this association does not show a link directly between the two.

In the United States, approximately 1 in 36 children are diagnosed with autism spectrum disorder (ASD) each year, according to data from the U.S. Centers for Disease Control and Prevention.

Scientists still don’t know the exact cause of autism, a developmental disorder. Genetics may be a factor, but some also look at potential environmental causes.

Cases may be increasing, but that’s also not clear. A study published this year of cases in the New York and New Jersey area found that autism diagnosis rates tripled in some age groups between 2000 and 2016. A 2021 report found a similar increase cases, but the CDC says the increase in cases is the largest. likely linked to more doctors screening for the disease.

Lithium is an alkali metal found naturally in some foods and groundwater. It is used in batteries, greases and air conditioners, as well as in the treatment of bipolar disorder and certain blood disorders. Its levels in drinking water in the United States are not regulated, according to the US Geological Survey.

A new study, published Monday in the journal JAMA Pediatrics, found a small association between lithium and autism diagnosis in Denmark, where researchers say the level of lithium in drinking water is similar to that in water systems. American water.

Researchers checked a database of people with psychiatric disorders for children born between 2000 and 2013 to find information on 8,842 ASD cases and 43,864 non-ASD participants. They then measured the lithium concentration at 151 public water stations that served more than half of Denmark’s population and mapped where pregnant women lived.

As lithium levels in the water increased, the risk of an ASD diagnosis increased slightly. Specifically, compared to those at the lowest level of exposure, those with second and third exposures during pregnancy had a 24-26% higher risk of ASD. diagnosed in children. The highest exposure group had a 46% higher risk than those at the lowest exposure level.

The researchers couldn’t determine how much water pregnant women drank, but they chose Denmark in part because its residents consume one of the lowest amounts of bottled water in Europe.

Experts say it’s important to note that research cannot demonstrate that lithium exposure directly leads to an autism diagnosis.

More study is needed, said study co-author Dr. Beate Ritz, professor of neurology at the David Geffen School of Medicine at UCLA and professor of epidemiology and environmental health at the UCLA School of Medicine. public health from UCLA Fielding.

“Any drinking water contaminant that may affect human brain development deserves careful consideration,” Ritz said in a news release. She added that the research should be replicated in other countries to look for a similar link.

The implications of these findings are complex when it comes to public health policy, according to an editorial published alongside the study. Lithium levels in water, at concentrations that the study associates with potential ASD risk, have also been linked to health benefits, such as decreased rates of hospitalization for psychiatric disorders and suicide .

“If all of these associations are valid, the wisdom of Solomon will be needed to develop guidelines for lithium in drinking water that are maximally protective of the entire population,” wrote Dr. David C. Bellinger, professor of neurology and psychology at Harvard. Medicine School. “Until the fundamental biology of ASD is better understood, it will be difficult to distinguish causal from spurious associations. »

Dr. Max Wiznitzer, director of the Rainbow Autism Center at Rainbow Babies and Children’s Hospital in Cleveland, points to other research on the effects of lithium on pregnant women who take it for mental health conditions. These studies – which involve people exposed to levels much higher than those found in drinking water – do not show a link with autism spectrum disorders.

“It’s an interesting association, but causation is certainly not proven,” said Wiznitzer, who was not involved in the new research. “We need to see if there is a viable, biologically plausible mechanism by which a small amount of lithium in the water supply can somehow do this, but it has not been reported that l “Pharmacological administration of lithium to women with bipolar disorder results in an increased risk of ASD.”

Other studies have also suggested links between ASD and environmental exposures to things like pesticides, air pollution, and phthalates. But none of them point to any of these factors as a direct cause of the disorder.

A link between environmental exposure and ASD is difficult to prove, Wiznitzer said. While research shows that increased exposure to air pollution increases the risk of giving birth to a child with ASD, for example, it is often questioned whether pollution is the driving factor or whether it is just the populations who live in more polluted areas.

“There is a lot of speculation about environmental factors, but how many of them are actually causally related? » said Wiznitzer. “We are bombarded with various environmental stressors in our daily lives. We need to figure out how to navigate them safely, and that’s probably not the one at the top of our list.