There's no proof that stress by itself causes long-term high blood pressure. But reacting to stress in unhealthy ways can increase your risk of high blood pressure, heart attacks and strokes. How common is prehypertension? Prehypertension is between 120-139 for the first number in your blood pressure reading, and/or 80-89 for the second number. Nearly 30% of American adults have prehypertension, according to the CDC. What's the risk? You're more likely to get high blood pressure (hypertension).