A new study has found a potential link between the amount of lithium within the water supply and higher rates of autism in the population, marking one of the first times lithium has been associated with autism risk. The study of data from Denmark suggested that pregnant women whose tap water had more lithium showed an increased risk of their children being diagnosed with autism by almost 50 percent for the highest exposures. However, causation has not been proven yet.
“Any drinking water contaminants that may affect the developing human brain deserve intense scrutiny,” said lead study author Beate Ritz in a statement.
“In the future, anthropogenic sources of lithium in water may become more widespread because of lithium battery use and disposal in landfills with the potential for groundwater contamination. The results of our study are based on high-quality Danish data but need to be replicated in other populations and areas of the world.”
Lithium is currently used in a range of medications under the brand names Priadel, Camcolit, Liskonium, and Li-Liquid, owing to its mood-stabilizing effects and use in treating mania. It is typically prescribed for depression and bipolar disorder, but current recommendations state people who are pregnant or planning to get pregnant should not take lithium as it may increase the likelihood of miscarriage and birth anomalies.
While it has been documented that lithium may affect fetal development, whether it affects the neurological development of fetuses is poorly understood, despite our knowledge of lithium's numerous neurological effects on the person themself. Previous research has highlighted lithium as a potential factor in neurological anomalies and autism, and researchers from the University of California-Los Angeles looked to identify a stronger link.
Taking data on 151 public water supplies in Denmark, the researchers looked at which suppliers provided water to pregnant people during their term, before comparing that data with births across the study time. There were 12,799 children diagnosed with autism and 63,681 children without an autism diagnosis during the time.
After controlling for variables that may impact the risk of autism, the researchers discovered that autism rates rose with the amount of lithium in the water. Compared to the lowest quartile, the second and third quartiles had a 24-26 percent higher risk of babies born with autism, while the highest quartile had a 46 percent increased chance. The risk was higher in urban areas compared to rural areas.
The paper does well at controlling for variables such as sex and age, but with autism spectrum disorder (ASD) being such a complex disorder, it is almost impossible to establish true causation.
As experts explain, ASD diagnoses vary greatly depending on how available healthcare services are in the area, and the researchers do not provide a location map to correlate lithium levels with access to mental health services.
"What the study really does is [look] for associations between lithium levels in the water around the mother’s address during pregnancy, and the likelihood of her child being diagnosed with autism in the first three to 16 years of life," Dr Rosa Hoekstra from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, told Science Media Centre. "That likelihood may be higher if you live near good autism diagnostic services."
Experts urge caution when interpreting this data, as it is such a contentious and impossibly difficult area to study. Further results are needed to identify if the link between lithium and autism is really there, and significantly more will be needed to show causation.
The study does, though, begin an interesting conversation about a possible new environmental factor in a very complex disorder.
The research is published in JAMA Pediatrics.