In our recent as yet unpublished work at Swansea Sleep Lab we have woken sleepers in the lab and asked them for dream reports from REM and deep Slow Wave Sleep. They had kept a 10 day diary before coming to the lab. We later asked them to identify items in the diaries that matched the dream content. We found that items that were incorporated into dreams were more emotional than items that were not incorporated.
Ernest Hartmann wrote in his book The Nature and Functions of Dreaming (OUP, 2011) that we can dream of waking life emotional events either directly or metaphorically.
This has now been shown by the following experiment.
In Davidson and Lynch a high impact film of the events of 9/11 and a non-emotional educational film were shown to participants. The critical waking life event was thus experimentally determined, to control for post hoc confabulations between dream content and prior events. There were more literal, closely associated and distantly associated (i.e., non-literal) references to 9/11 after the 9/11 video than after the education video, but the most significant difference was in distantly associated references. There was more fear, sadness, and shock, and less joy, contentment and excitement in dreams after seeing the 9/11 film than after the education film. This suggests dream content has literal and associative or metaphoric content.
Davidson, J., & Lynch, S. (2012). Thematic, literal and associative dream imagery following a high-impact event. Dreaming, 22, 58-69. http://dx.doi.org/10.1037/a0026273