Sorry, that's wrong, at least as far as caffeine is concerned, and certainly as far as adverse behavioural effects ("behavioural toxicity") are concerned in humans.
That Kang et al. study was 50mg/kg of caffeine administered three times a day. That would be about a hundred cups a day of coffee for my body weight. Don't they say the dose makes the poison?
Curse you science! Still, this is just in rats. Rats with their weak rat brains. My superior human brain can easily absorb this caffeine with no ill effects!
No idea on that front. The caffeine one struck a chord because I'm a slow metaboliser, and it can cause me issues with anxiety under the wrong circumstances. It does make me wonder how many cases of anxiety are at least exacerbated by genetic issues with processing caffeine and other stimulants.
> Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specifically, a neurotoxin or neurotoxicant– alters the normal activity of the nervous system in such a way as to cause permanent or reversible damage to nervous tissue.
Brain cells getting killed is a normal process, you could call it pruning. Cells grow back, you know!
So do coffee, tobacco, antidepressants and antipsychotics.