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

A 2023 study published in JAMA Pediatrics analyzed 8,842 autism spectrum disorder (ASD) cases and 43,864 controls born in Denmark between 2000 and 2013, finding a small association between higher lithium levels in public water supplies and increased ASD diagnosis risk. Compared with the lowest exposure group, those with second and third highest exposure during pregnancy had a 24% to 26% higher risk of ASD, and the highest exposure group had a 46% higher risk. The research examined lithium concentrations in 151 Danish waterworks serving over half the population. Experts caution this association does not prove causation, noting that lithium levels in drinking water are much lower than therapeutic doses used for bipolar disorder, which haven't shown ASD links. The study authors call for replication in other countries due to lithium's complex implications - while potentially linked to ASD risk at these concentrations, similar levels have also been associated with lower rates of psychiatric hospitalization and suicide.