MONDAY, April 3, 2023 (HealthDay News) -- There's no single known cause for autism, but researchers now point the finger at higher lithium levels in drinking water.
Their new study found that pregnant women in Denmark whose household tap water had higher levels of lithium were more likely to have kids with autism, compared to pregnant women living in areas where tap water had lower levels of this element.
Autism is characterized by problems with social interaction, communication and behavior. About 1 in 36 children in the United States have the disorder, according to the U.S. Centers for Disease Control and Prevention. April is Autism Awareness Month.
“Maternal prenatal exposure to lithium from naturally occurring drinking water sources in Denmark was associated with an increased autism spectrum disorder risk in the offspring,' said study author Dr. Beate Ritz, a professor of neurology at the David Geffen School of Medicine at UCLA. “This suggests a potential fetal neurotoxicity of lithium exposure from drinking water that needs to be further investigated.”
Lithium leaches into drinking water from soil and rocks, but these levels could rise in the future from waste in lithium batteries that are not disposed of properly.
“Lithium interferes with neurodevelopment during pregnancy and early infancy,” Ritz said. A biological pathway called WNT signaling plays a role in brain development and autism, and the pathway is also affected by lithium in animal models, she noted.
While more research is needed to confirm this association, Ritz suggested using filtered water and testing it for lithium levels while pregnant.
Bottled water isn’t necessarily the answer. “A lot of bottled water is not tested either,” she said. “[Some] bottled water is just filled up from regular drinking water sources.”
Lithium levels in Denmark’s water are likely in the low to moderate range, Ritz added. But a 2021 study from the U.S. Geological Survey found that about 45% of public wells and about 37% of U.S. domestic supply wells have concentrations of lithium that could present health risks.
For this latest study, researchers analyzed lithium levels in 151 public waterworks in Denmark, representing about half of the country's water supply. They then used address information from Denmark’s civil registry system to see which waterworks supplied women’s homes when they were pregnant.
When the investigators compared children with autism to those without this developmental disorder, they found that when lithium levels increased, so did the risk of autism.
Kids born to moms who lived in areas with the highest lithium levels in the water were 46% more likely to be diagnosed with autism than those born in areas with the lowest amount of lithium in drinking water, the study showed.
The findings held when researchers controlled for other factors known to affect autism risk, such as maternal age and smoking status during pregnancy. Lithium levels increased the risk for all types of autism in this study.
Lithium as a medication is also used to treat depression and bipolar disorders. There has been debate about whether pregnant women can safely take lithium due to the possible increased risk for miscarriage or birth defects. Other research has linked lithium from drinking water to adult-onset neuropsychiatric disorders.
The study appears in the April 3 issue ofJAMA Pediatrics.
"If all of these associations are valid, the wisdom of Solomon will be required to develop guidelines for lithium in drinking water that are maximally protective of the entire population," David Bellinger, a professor of neurology and psychology at Harvard Medical School, told CNN. “Until the basic biology of ASD [autism spectrum disorder] 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, urged caution before jumping to conclusions. Research that looked at pregnant women who take lithium for mental health disorders doesn’t show a connection with autism, and these women are exposed to much higher levels of lithium than what would be found in tap water.
“It’s an interesting association, but causation is definitely not proven,” Wiznitzer told CNN. “We have to see if there’s a viable and biologically plausible mechanism by which a small amount of lithium in the water supply can somehow do this, yet pharmacologic dosing of lithium in women with bipolar disorder has not been reported to be causing increased risk of ASD.”
The U.S. Centers for Disease Control and Prevention has more on autism.
SOURCES: Beate Ritz, MD, PhD, professor, neurology, David Geffen School of Medicine, UCLA, professor, epidemiology and environmental health, UCLA Fielding School of Public Health, Los Angeles; JAMA Pediatrics, April 3, 2023, CNN