Can a person raise their blood pressure reading just by thinking about it rising?

Yes: That can happen when a person with high blood pressure checks his BP (to write it down), and notices that it is higher than he wants it to be. He thinks about it and takes it again, but it turns out a few points higher than before. Then, he thinks about it some more, and takes it a third time, but now it's even higher... So, the more he thinks and worries about it, the higher the BP goes.