A woman is counselled by a police officer
Researchers say "image rehearsal therapy" greatly improved the amount of sleep that women were able to enjoy.
Traditionally, even though women with post-traumatic stress disorder following rape or sexual abuse do suffer nightmares, doctors tend to treat other symptoms of the disorder rather than focus on the nightmares themselves.
However, Dr Barry Brakow and colleagues at the Sleep and Human Health Institute in Albuquerque, New Mexico, looked at a group of 168 women, most of whom had suffered a rape or serious sexual assault.
Most had also been repeatedly abused as a child or adolescent.
Instead of only dealing with other symptoms, such as depression or intrusive thoughts, Dr Brakow coached the women in "dream therapy".
Nightmares
This involved thinking of pleasant images, then thinking of the type of nightmare they might suffer, and imagining a different, more pleasant, outcome or ending.
Then this new "nightmare" was rehearsed mentally for between five and 20 minutes a day.
Many of the women found that not only were their nightmares less frequent, but that overall their sleep improved and other post traumatic stress symptoms got better as well.
Dr Brakow said: "Perhaps by decreasing bad dreams and improving sleep quality, post-traumatic stress disorder patients improve daytime energy, which facilitates coping with other distress symptoms."
The research was published in the Journal of the American Medical Association.