One word.........alcoholism.
Been there; know the feeling (UGH; so frustrating,etc,etc) .........guess that is why we can't pay attention to them and their responses; there is no rhyme or reason to what they think,say or do...it's a crap shoot they don't know or understand,either. They are under the influence of chemicals. If we do; we are under the influence of them while they are under the influence of chemicals.............