This is my experience. In fact, it seems many of my dreams are ‘disturbing’ but usually not overly so. A few months ago I thought about this and was a bit depressed wondering what ever happened to my good, happy dreams.
The closest to a ‘nightmare’ (and not really that close) are the very annoying ‘my teeth are falling out’ dreams. I hate HATE HATE those!
On the good side, I haven’t had a late for a test/forgot to drop a class and need to take the final type dream in a few years…it just took 20 or so years after Grad school for those to stop!