I had a dream when I was in a dark room and then it was just black and I felt it envelop me and I woke up in a cold sweat.
Personally I don't fear darkness itself. In fact, I sometimes feel satisfaction in it. What people often fear are the things they think that lurk within the dark or the feeling of claustrophobia.
When I was a little boy, I admit that I am scared of the dark. Especially alone in the darkness. But, in my adulthood, it's totally gone. I am not scared anymore today. Fear in the darkness can cause intense symptoms of anxiety and depression. A fear becomes a phobia when it's excessive, irrational, or impacts on your day to day life.