The tendency to suppress, inhibiting thoughts, and dream rebound.

Ironic control theory proposes that suppressing thoughts leads to increased occurrence of the suppressed thought because monitoring for the unwanted thought leads to intrusions. This study investigated the influence of suppressing unwanted thoughts on dream content. One hundred participants who had high or low levels of tendency to suppress unwanted thoughts nominated an intrusive thought, and half of the participants were instructed to suppress that thought for 5 min prior to sleeping. Participants completed a dream diary upon waking, which was subsequently rated by independent raters for dream content. In terms of the 79 participants who reported dreaming, more high suppressors who were instructed to suppress dreamt about the intrusive thought than high suppressors in the control condition. There was no difference between low suppressors in the suppression and control conditions. These results suggest that dream content can be influenced by attempted suppression prior to sleep, and this is particularly apparent in people with a tendency to suppress unwanted thoughts.