The Interpretation of Dreams by Sigmund Freud Chapter 7 Page 24

The determinations for its realization consist in the fact that repressions have taken place, and that the suppressed emotional wishes shall become sufficiently strong. They thus stand entirely without the psychological realm of the dream structure. Were it not for the fact that our subject is connected through just one factor, namely, the freeing of the Unc. during sleep, with the subject of the development of anxiety, I could dispense with discussion of the anxiety dream, and thus avoid all obscurities connected with it.

As I have often repeated, the theory of the anxiety belongs to the psychology of the neuroses. I would say that the anxiety in the dream is an anxiety problem and not a dream problem. We have nothing further to do with it after having once demonstrated its point of contact with the subject of the dream process.