Small associations from ecological studies are questionable whether the effect is negative or as in this case positive.
Fajardo VA, LeBlanc PJ, Fajardo VA. Trace lithium in Texas tap water is negatively associated with all-cause mortality and premature death. Applied physiology, nutrition, and metabolism 2017 Dec 5. doi: 10.1139/apnm-2017-0653.
Lithium in tap water was previously found to have life-extending effects across 18 Japanese municipalities. Using a larger dataset with several Texas counties, our study shows that lithium concentrations in tap water are negatively associated with all-cause mortality (r = -0.18, p = 0.006, 232 counties) and years of potential life lost (r = -0.22, p = 0.001, 214 counties). Thus, our present findings extend and reinforce lithium’s purported life-prolonging effect in humans.