From Scientific American article

The results found this treatment [see article for details] to sig­nificantly decrease feelings of being con­taminated and also—to the researchers’ surprise—overall post-traumatic distress scores. Study author Kerstin Jung says the combination of factual information with mental imagery is key because the information alone can leave a patient knowing the facts but not feeling they are true on an emotional level. At that point, “we introduce the imagery technique as a vehicle to transport the rational information from the head to the heart,” she says. “Images are much more powerful to change emotions than verbal information.”