There have been studies linking naturally high lithium levels in groundwater to lower suicide rates. It stabilizes moods for anyone not just those with a bipolar diagnosis. For me it’s most noticeable in regulating anger/rage outbursts. Studies also indicate that it’s neuroprotective - reducing risk or severity of dementia, Alzheimer’s, and Parkinson’s.

Natural fluoride is associated with better dental health, so I'd imagine it is associated. (Within safe levels, of course, just like how too much fluoride turns your teeth brown and gives you brain damage.)