As the more careful commentors suggest, a medical/physical disposition toward a particular behaviour can be one factor in a "familial trait," although in this case "feudin' an' fightin'" was something of a local tradition in the area.

The one "most ignorant" comment:

Medical folks like to find these kinds of explanations. Like the Salem witchcraft thing. That book came out about how that was caused by wheat that was grown that had this parasite or mold or fungus or something that caused everybody in Salem to go nuts," she said.

That is personally offensive, since I first proposed the ergotamine theory of the Salem witches when I matched up symptoms cited in gran'pappy's 1898 veterinary manual - for the behaviour of sheep with ergot poisoning - with the "witches" behaviour cited in the early Salem transcripts, (ca. 1948). As nobody much listened to a 9 year old kid, it was several decades before "the book" was published, although I thought it was "common understanding" for most of those several decades.

And:

1. the people in Salem didn't grow wheat. They grew almost exclusively barley, which is much more susceptible to the ergot fungus than wheat is. A "historian" shouldn't make that mistake.

2. it wasn't a matter of the "whole town going nuts" (at least initially) but a matter of a few person behaving in ways that the people couldn't understand or explain - so that later on mob hysteria (never blamed on the fungus) took over. A "historian" shouldn't make that mistake either.

John