tormented by the certainty no one can hear
Classic unipolars were usually tormented by the conviction that no one else could hear or understand them when they tried to communicate. Hence jokes, sarcasm, the psychopathology of unconscious arm-rubbing.
Context
The isolation named as a symptom: the disease itself carries the conviction that one is unhearable, that every attempt to communicate fails at the far end, and the jokes and the arm-rubbing are the marks it leaves. The cruelty the scene closes on confirms her: nothing in the doctor's literature connects her episodes to what she is telling him, so her one real disclosure is filed under a question mark, "Then what?", as she finally weeps for real. The unipolar's certainty that no one can understand is met, here, by a method that structurally cannot.