In Shakespeare's Othello, psychological manipulation plays a key role in the development of the plot in the play. You have the main character and protagonist, Othello, who is eventually driven mad by Iago telling him false information and convincing him it is true. Iago is a clever man and he uses his cleverness to take advantage of a flaw that Othello has which is his jealousy. Iago's corruption of Othello plays a key part in the play because it leads to the death of himself and others. Othello had no true proof that Desdemona was having an affair but he still believes Iago. This just shows how naive Othello is. Othello also experiences seizures caused by stress and lack of sleep. He just can't believe that Desdemona would do that to him and he is embarrassed at the possible thought of being a cuckold.
On the other hand, Desdemona is going through some psychological problems as well. She lacks feeling of self-worth at this point in the novel because she doesn't known what she did to deserve punishment from Othello. It's a very rational thing to think about as a person in an abusive relationship that what did I do to deserve this? Desdemona and Othello suffer from depression right now because Othello thinks that Desdemona is cheating on him and Desdemona doesn't know why Othello is being so mean and nasty to her.