There are areas with high lithium levels in the water supply naturally.
but they won’t add it because it doesn’t work well except in those who are bipolar, who commit suicide on the “down” or depressed part of their cycle.
Lithium doesn’t really do much for normal folks or even for most cases of depression.
Lithium is used to treat mania which has often been thought of as the opposite of depression.
Other than making people lethargic
(The self-appointed overlord's would love that)
what possible use would it have?