I remember back in the day how opiates would cause extreme nightmares.
Now, I can't stand the thought of taking something like a morphine drug. I had surgery a few years back and wouldn't take the prescribed med, I let my self suffer! That's how bad the nightmares were.
I am not a psychologist, but I believe those nightmares (of mine) were an accumulation of paranoia brought on by drug use in general, coupled with all the terrible fears I had at that time.
Sometimes I believe it's my mind warning me.
I have had those anxiety dreams you mention. I am lost, or I am running away from a huge dog that's ready to pounce on me. For me, it's a signal that there's something I am not wanting to deal with. I usually realize what it is in a few days after really thinking about it.
One time it was credit card debt that was overwhelming me. That was the huge dog!!
I do hope you get some good sound sleep.
Here's a prayer for you...