My father is fairly normal , but he gets nervous easily and fast but that can be usual with some people , the problem is , sometimes I hear him swearing and cursing someone perhaps an imaginary person , but he does this when he's alone not with a family member , and when he senses that someone is coming he often sneezes and go back to his sanity , I just want to know what's wrong with him , he's in his 60s and he smokes A LOT .