Ancients claiming to hear "voices" of gods...

From what we know over the millenia, people who claim to be prophets have claimed that their various deities have spoken to them audibly. This is still sometimes used in modern day to argue for the existence of a deity. To me, this is problematic as an argument because from what certain archeologists know, people in certain cultures used to consume things on a regular basis that we now know are harmful and poisonous to the human body..things like lead. I'll use the horrifically cruel emporer of Rome, Caligula, as an example. He became delusional and heard voices quite a bit, and even thought he himself was a god because of these delusions. He also actually ATE and DRANK lead on a regular enough basis that modern-day scientists have been able to concur that he would be suffering from very severe and even deadly lead poisoning towards the end of his rule/life...had he not been assassinated, he would have expired in due time because of lead poisoning, which does mentally leave a person extremely delusional. I'm wondering if prophets and such in ancient times were also exposed to deadly toxins of sorts that could have contributed to them hearing the voices of deities. Just something to think about...I'm not saying it's "the" conclusive reason for all prophets hearing voices (they could have just knowingly been making shit up as well), but it's something that's crossed this Atheist's mind...