Is Being A Liar Genetic? What About Alzheimer's?

Obviously this doesn't have any direct bearing on McCain's fitness for the presidency, unlike his offshore drilling lies and his ignorance on basic facts about Iraq, but I think it, in conjunction with many other examples, helps paint a picture about McCain's character--more specifically, in this case, he either has Alzheimer's or he is a pathological liar. I'm still undecided, I think it is probably a bit of both. But you decide.