Mental Illnesses In Shakespeare's Time.

Shakespeare was a keen observer of human behavior. And he even noted a couple of mental illnesses before we had words for them. For example, Hamlet was obviously bipolar. Like this exchange in Act III, Scene 2 with Ophelia shows:

“Lady, shall I lie in your lap?”
“No, my lord.”
“I mean, my head upon your lap?”
“Ay, my lord.”
“Do you think I meant country matters?”
“I think nothing, my lord.”
“That’s a fair thought to lie between maids’ legs.”
“What is, my lord?”
“Nothing.”
“You are merry, my lord.”
“Who, I?”
“Ay, my lord.”

And Lady Macbeth obviously had OCD. When she was seen constantly washing and rewashing her hands in that play. Shakespeare noticed noblewomen cleaning and dusting all day long around their palaces. He knew it had no logical purpose. So he thought maybe they were mad. Or suffering from the mental illnesses bipolar disorder and OCD, as we'd say today.