Overnight Therapy: How Unpleasant Dreams May Be Good for You

Could dreaming about unpleasant thoughts be adaptive?

Posted Mar 20, 2019

The “dream rebound” effect refers to the finding that when participants suppress a thought prior to sleep, that thought and related emotions/cognitions are more likely to appear in dreams reported the next morning. [See previous post.] The effect has been replicated in several studies, particularly for unpleasant thoughts. Nevertheless, whether the dream rebound impacts subsequent waking thought is unknown. Could the dream rebound be adaptive in some way? Or is it maladaptive, a form of intrusion into a sleep that could be distressing?

A recent study set out to investigate whether the emotional tone of suppressed thoughts impacts dream rebound and whether dream rebound then impacts waking thought.

Seventy-seven participants completed the study, which involved three parts: First, participants completed a series of questionnaires on factors that relate to thought suppression (neuroticism, depression/anxiety). Then, for seven days, participants completed an evening suppression task and a morning dream diary each day. Finally, at the end of the study, they were asked some questions about how they felt about their target thought.

The evening suppression task asked participants to select a personally relevant thought – either pleasant or unpleasant depending on which condition they had been assigned to. They were asked to spend five minutes attempting to suppress the thought, and, at the same time, write a stream-of-consciousness on a piece of paper and mark a check anytime the thought popped into their head. This task measures how successful a participant is at suppressing their thought, based on how many check marks are made. In the morning, participants reported their dreams. These dreams were later rated by independent judges on whether they related to the target thought on a scale of 0 (not at all) to 4 (strongly related).

Finally, both at the beginning and the end of the study, participants were asked to rate how pleasant/unpleasant their target thought was, as the researchers were also interested in whether there would be any change in emotional response to the thought over the course of the experiment.

Overall, participants reported on average 7.26 dreams, and this did not differ between unpleasant and pleasant thought suppression conditions.

As mentioned, the authors measured how many times the target thought popped into mind during the suppression task, according to the participants' check marks; but there was no difference in intrusions between the two conditions – in other words, participants were equally capable of suppressing pleasant and unpleasant thoughts during wakefulness. Unpleasant thoughts, however, were dreamt of more often than pleasant thoughts – the dream rebound thus seems more likely to occur for unpleasant thoughts suppressed prior to sleep.

Finally, the authors wanted to see how dream rebound impacted waking thought. For this analysis, participants were split into groups depending on how much they dreamt of the suppressed thought – there was a group high in dream rebound (dreamt a lot about the suppressed thought) and low in dream rebound (did not dream much of the suppressed thought). 

When the suppressed thought was unpleasant, participants who did not dream much about the thought subsequently rated the thought as being more unpleasant; participants who dreamt a lot about the suppressed thought comparatively rated their thoughts as more pleasant, suggesting that the dream rebound had beneficial effects on participants' emotional response to the thought.

For pleasant thoughts, participants low in dream rebound reported lower pleasantness than participants high in dream rebound, again suggesting that dreaming of a suppressed thought offers a therapeutic effect.

In sum, "dream rebound" is stronger for unpleasant than pleasant thoughts — unpleasant thoughts were more likely to appear in dreams following suppression attempts. Participants who dreamt more of their suppressed thought rated it as more pleasant later on, which is in line with emotion-processing theories of dream function — that emotional experiences are processed during dreams and this ameliorates emotional responses following sleep. [See previous post.]


Malinowski, J., Carr, M., Edwards, C., Ingarfill, A., & Pinto, A. (2019). The effects of dream rebound: evidence for emotion-processing theories of dreaming. Journal of sleep research, e12827.