Lithium levels in tap water may be linked to an increased risk of autism spectrum disorder (ASD) in children born to pregnant women exposed to higher concentrations. 
Researchers have found a modest association between lithium exposure and ASD diagnosis in Denmark, where the level of lithium in drinking water is similar to that in US systems. The study, published Monday in JAMA Pediatrics, analyzed data from 8,842 cases of ASD and 43,864 participants who did not have ASD. The results showed that as lithium levels in water increased, so did the risk of an ASD diagnosis.
Those exposed to higher concentrations had a 24% to 26% higher risk compared to those at lower exposure levels. In contrast, pregnant people who drink bottled water may be more likely to have their water tested for lithium and are less likely to consume tap water with high lithium levels, according to experts.
The study's lead author says the research can't show that lithium exposure leads directly to an autism diagnosis. The results suggest that further study is needed to look for a similar connection in other countries and more research is required to determine if there is a biological mechanism by which small amounts of lithium in tap water can increase ASD risk.
Other studies have suggested connections between ASD and environmental exposures to pesticides, air pollution, and phthalates. However, none point to any of these factors as a direct cause of the disorder. The study highlights the complexity of determining whether there is a causal link between an environmental exposure like lithium in tap water and a developmental disorder like autism.
The implications of this finding are complex for public health policy. While lithium levels in drinking water have been linked to lower rates of hospitalization for psychiatric disorders and suicide, the exact mechanism by which small amounts of lithium may increase ASD risk is still unknown.
				
			Researchers have found a modest association between lithium exposure and ASD diagnosis in Denmark, where the level of lithium in drinking water is similar to that in US systems. The study, published Monday in JAMA Pediatrics, analyzed data from 8,842 cases of ASD and 43,864 participants who did not have ASD. The results showed that as lithium levels in water increased, so did the risk of an ASD diagnosis.
Those exposed to higher concentrations had a 24% to 26% higher risk compared to those at lower exposure levels. In contrast, pregnant people who drink bottled water may be more likely to have their water tested for lithium and are less likely to consume tap water with high lithium levels, according to experts.
The study's lead author says the research can't show that lithium exposure leads directly to an autism diagnosis. The results suggest that further study is needed to look for a similar connection in other countries and more research is required to determine if there is a biological mechanism by which small amounts of lithium in tap water can increase ASD risk.
Other studies have suggested connections between ASD and environmental exposures to pesticides, air pollution, and phthalates. However, none point to any of these factors as a direct cause of the disorder. The study highlights the complexity of determining whether there is a causal link between an environmental exposure like lithium in tap water and a developmental disorder like autism.
The implications of this finding are complex for public health policy. While lithium levels in drinking water have been linked to lower rates of hospitalization for psychiatric disorders and suicide, the exact mechanism by which small amounts of lithium may increase ASD risk is still unknown.