How are Macbeth and Lady Macbeth presented as mentally disturbed?

Aside from the fact that killing for power is in itself a form of mental unrest, there are many times in the play where each of them seem to have lost their minds. The most clear evidence is Lady Macbeth, who becomes insane with guilt. She continually tries to wash the blood from her hands, crying "Out damned spot!" when of course there is actually no blood on her hands at all. This is a sign of how her horrible actions have brought her to madness.

Macbeth himself grows increasingly paranoid and also shows sings of insanity. Banquo's ghost may not be real, since only Macbeth is able to see it. This suggests that perhaps it is an illusion and that he too is suffering from hallucinations brought on by guilt and madness. Combine this with the couple's horrible actions and and we begin to see how these two people are clearly mentally unwell.