Not so sick, my lord,
As she is troubled with thick coming fancies,
That keep her from her rest.

– William Shakespeare

Macbeth, Act 5, Scene 3. The Doctor gives his diagnosis when Macbeth asks how is his patient Lady Macbeth. In his opinion she is not physically ill, but mentally disturbed by nightmares and visions that keep her from sleeping. The quote also shows Lady Macbeth’s guilt over her husband’s murders.