Li+ as a nutrient (1-5 milligrams per day) must not be confused with lithium as a drug, prescribed to clinical patients 100-300+ milligrams per day. It is an effective drug simply because it is, first and foremost, an essential mineral, just like sodium or potassium.
I’ve supplemented since 2016 with Li+, because like most Americans, I’m probably not getting enough in my diet.