Perhaps, but if it's having a mental effect of notable size it still causes me concern. If you're happy with your current behaviors I don't see why you'd want it. Wouldn't it be better for individuals to just opt to take it themselves, encourage usage of those already existing environmental sources, etc?
Iodine is added to table salt for the same effect. Although I am no fan of too many additives, I do approve this practice. I wonder if it would be feasible to institute today...
Iodised salt is easy to opt out of though, many salts come without it still. Your municipal tap water is much harder to opt out of. Which is why I'd suggest you simply allow people to add this themselves if they'd like.
My close experience with depression (not myself) is that it can takes years for someone to accept the thought of being depressed, and even more time to seek help.
Sadly, there's too much prejudice and taboo over mental health in our society. People treat it as a badge of shame, not a disease.
