How did Macbeth's mental health deteriorate?
William Shakespeare’s Macbeth is the story of a man whose fledgling ambition makes him susceptible to manipulation, which then grows into an insatiable appetite for power. If we want to look at how his mental health deteriorates, we have to look at what causes the problems that push Macbeth over the edge. Macbeth’s mental health is adversely affected because he is manipulated to act not in accordance with his own will, but with the will of others.
Initially, Macbeth is manipulated by the witch’s prophecy that he will be king. Although this was never his ambition, he begins to obsess over it, and tells his first lie to Banquo when he says of the witches and their prophecy:
I think not of them.
A little later, he is manipulated by Lady Macbeth, who convinces him to kill Duncan. At this point Macbeth’s mental health is reflected in the guilt he feels even before the murder, when his speaks of his vision of the dagger:
I see thee still;
And on thy blade and dudgeon gouts of blood,
Which was not so before.
Once Macbeth starts making decisions for himself, the audience can see that he has been transformed from a noble thane to a fiend. He kills Banquo and tries to kill his son; he kills the whole of Macduff’s family, children and all; he seeks out the counsel of the witches again and falls for their trap.
If Macbeth had followed his own instincts and not allowed himself to be duped by the witches and Lady Macbeth, his mental state would have been unaltered. By subjugating his will to that of someone else, he sacrifices his own mental health and his own destiny.
It is in Act II, Scene I that Macbeth's mental deterioration really begins. After agonizing over whether or not he should kill Duncan, Macbeth has his first hallucination: he sees a bloody dagger which leads the way to Duncan's bedchamber.
Hallucinations are a defining feature of Macbeth's mental downward spiral. In Act III, Scene IV, for example, Macbeth has a hallucination in which he sees Banquo sit in his seat at the banquet. Unlike the first hallucination, the vision of Banquo prompts obvious and considerable mental anguish for Macbeth. During this banquet, for instance, he raves at Ross about an empty seat and appears so frightened that Lady Macbeth has to apologize to his guests.
By Act IV, Macbeth is so paranoid and afraid of losing his crown that he visits the witches again and demands that they answer his questions about the future. This temporarily reassures Macbeth, since they tell him that he can be harmed by "none of woman born."
In the final act, however, Macbeth's deterioration is complete. In Scene IV, for example, Macbeth admits that nothing can scare him anymore, because he has experienced all the horrors that a man could experience:
I have supped full with horrors.
Direness, familiar to my slaughterous thoughts
Cannot once start me.
Finally, on hearing the news that Lady Macbeth has died, Macbeth is devoid of any real emotion. He has experienced so much guilt and distress that life has lost all meaning. His downward spiral is, thus, complete.
There are a few different stages to Macbeth's mental deterioration. In Act II, we see Macbeth nearly paralyzed with guilt over the murder of Duncan. We understand that, while he is ambitious, regicide was not his intended plan for gaining power. In Act III, we see the growth of his guilt. He thinks he sees Banquo at the dinner table, when he knows that Banquo is dead. He speaks to the ghost, not realizing at first that everyone cannot see him. Eventually, Lady Macbeth has to break up the dinner party, excusing her husband for being ill. In Act IV, out of desperation, Macbeth visits the witches again and demands to know more. Feeling empowered by their prophecies, he embraces battle with Malcolm. He feels like he is undefeatable, and using that feelings to let his hungry for power consume him, making him mad with power. Ultimately, he is forced to face reality in his battle with Macduff, which ends with his death.