Thought suppression produces a rebound effect with analogue post-traumatic intrusions

Attempts to suppress traumatic material may be involved in the development and maintenance of post-traumatic stress disorder (PTSD). In order to investigate this possibility, analogue post-traumatic intrusions were induced in normal participants by means of a distressing film. For comparison, a second film was used to induce intrusions about polar bears. It was hypothesized that the suppression of these intrusions would produce an immediate decrease but a delayed increase ("rebound effect") in their frequency. It was also predicted that the rebound effect would be larger for the analogue traumatic intrusions. Each film was followed by two consecutive time periods during which participants' thoughts were recorded. During the first period, the suppression group was instructed to suppress thoughts about the film whilst the control group merely recorded their thoughts. During the second period, both groups merely recorded their thoughts. The results supported the immediate decrease hypothesis for both types of intrusion. As predicted, there was a rebound effect for analogue traumatic intrusions although not for polar bear thoughts. Several methodological issues relating to the findings are highlighted. The possible implications of a rebound effect with trauma-relevant intrusions are discussed with reference to PTSD.