In the most recent and comprehensive study so far on the topic, Mevagh Sanson and colleagues systematically and empirically examined the consequences of trigger warnings for three symptoms of people’s distress: (1) negative affect following exposure to negative material, (2) intrusive thoughts related to the negative material, and (3) avoidance of reminders of the negative material. Across six experiments, they presented some people (but not others) with a trigger warning, exposed everyone to distressing material, and measured their symptoms of distress. Then they conducted summary statistics on the overall data (totaling 1,394 people) to estimate the effect size of trigger warnings.

They found that people who saw trigger warnings judged the material to be just as negative, felt similarly frequently intrusive thoughts and avoidance, and understood subsequent material just as much as those who did not see trigger warnings. Whatever positive effects of trigger warnings that were found were “so small as to lack practical significance.”

Their findings are consistent with the idea that over-accessible memories of traumatic experiences can contribute to symptoms of PTSD, and are also consistent with the idea that the same cognitive processes are at play during traumatic experiences of differing levels of severity.