Thrillers are for thrills, not vague irritation
Picture the scene; you are watching a film that has been branded a 'psychological thriller'. You know, then, that whatever the main aggravation for the protagonist, it is going to be something inside their own head. Knowing this, a good director will have tried to integrate a little mystery as to what this mental affliction might be and keeps you guessing. It could be agoraphobia, or claustrophobia. Something is going to tip this character over the edge - the interest lies in what it is, what has caused it and what inevitable tragedies it will cause.
