Lithium is used to dull people's minds, a psychosuppressant.

Yes, but you don't need industrial mining for that. It is negligeable quantities and even ineffective processing of sea water will be more than enough to supply that demand.

Meanwhile you could easily detect even tiny amount of lithium salts in food using gas torch or gas stove. Lithium paint flame into bright red color. If you have lithium in food, then if you put a small piece of it into blue gas flame it will become bright red.