The theory that lead poisoning hastened the fall of the Roman Empire was once in vogue, but there's been some debunking of this notion in recent years.
See:
http://news.sciencemag.org/archaeol...ancient-romeEven if it was true the Roman patricians suffered from excessive exposure to lead, which can have effects on cognition and behavior, I'm not sure there's any clinical evidence that would link it to insanity per se. I'm more inclined to attrribute the seeming madness of figures like Caligula and Nero to Lord Acton's observation that "absolute power corrupts absolutely."
Commodus, though, in addition might've been, as they say, "not wrapped too tight."
Here's a sculpture depicting him with his preferred Herculean accoutrements -

Colligo ergo sum
Edited by Lucky Cuss
01/19/2016 08:02 am