University students are requesting, and many of their professors are issuing, “trigger warnings.” Trigger warnings are a kind of content warning; they give a précis of the material to follow and caution that it may cause a reader or viewer to experience symptoms of distress. The use of these trigger warnings in higher education is controversial: Their purpose is to reduce or eliminate the distress students may otherwise experience in response to “triggering” course content, but no data exist regarding how effective they are at achieving this purpose. Moreover, there is reason to suspect these warnings may backfire and exacerbate the very symptoms they are intended to alleviate. We conducted the first investigation into the effects of trigger warnings: We gave some subjects a trigger warning, but not others, then exposed all of them to negative material, and measured the analogue symptoms of posttraumatic stress disorder they experienced. Meta-analyses on data gathered across our six experiments revealed that trigger warnings had trivial effects—regardless of if subjects had seen a trigger warning beforehand, they judged the material to be similarly negative, and reported similar levels of negative affect, intrusions, and avoidance. These results suggest that trigger warnings are neither meaningfully helpful nor harmful, and that students and professors should not rely on them to mitigate students’ distress.