Can placebos prevent intrusive memories?

After traumatic experiences, intrusive memories can flash back and evoke significant distress. Here, we investigated whether the occurrence of intrusions can be prevented by placebo. After the exposure to an experimental psychopathology model of psychological trauma, healthy participants (N=112) were randomised to deceptive placebo (DP), open-label placebo (OLP), or a no-treatment control group. The results show that one week later, the groups did not differ in the frequency of intrusive memories. However, participants receiving OLP reported the lowest intensity of intrusions. Participants receiving DP reported the lowest burden of intrusions. Across groups, the expectation that intrusions will be intense and hardly controllable was associated with a higher frequency of intrusions, higher distress, higher burden, and more negative appraisal. The results suggest that expectations play a crucial role in the emergence of intrusive memories and that at least some of the disabling aspects of intrusive memories can be reduced by placebo.