How does blood pressure narrow or thicken arteries?
“Blood pressure” (hypertension) may be a result, but it is not a cause.
There are many different causes for hypertension, some of which aren’t understood at all, although effective medicines have been applied. Thickening or stiffening of arteries by plaque accumulation or aging are a couple of the causative factors. They can produce a hypertensive effect, but they are not the result hypertension.
An authoritative discussion of the disease is here: http://www.mayoclinic.org/diseases-conditions/high-blood-pressure/basics/causes/CON-20019580 (be sure to use the side menu tabs for detailed information).
Another popular information site with similar information is here: http://www.healthline.com/health/high-blood-pressure-hypertension