The effects of suppressing intrusive thoughts on dream content, dream distress and psychological parameters.

Suppressing unwanted thoughts can lead to an increased occurrence of the suppressed thought in dreams. This is explainable by the ironic control theory, which theorizes why the suppression of thoughts might make them more persistent. The present study examined the influence of thought suppression on dream rebound, dream distress, general psychiatric symptomatology, depression, sleep quality and perceived stress. Thirty healthy participants (good sleepers) were investigated over a period of 1 week. Half were instructed to suppress an unwanted thought 5 min prior to sleep, whereas the other half were allowed to think of anything at all. Dream content was assessed through a dream diary. Independent raters assessed whether or not the dreams were related to the suppressed target thought. The results demonstrated increased target-related dreams and a tendency to have more distressing dreams in the suppression condition. Moreover, the data imply that thought suppression may lead to significantly increased general psychiatric symptomatology. No significant effects were found for the other secondary outcomes.