Trigger warnings in classrooms are a beloved technique without a scientific basis. In fact, the studies that do exist indicate that trigger warnings in higher education do more harm than good. A newly-published literature review surveyed the mental health studies that are available, noting that "despite emerging momentum for the adoption of trigger warnings in the tertiary classroom, there has been little research conducted to date into whether the use of trigger warnings is in fact an effective strategy for effectively reducing traumatization." The researchers were not able to point to any rigorous studies finding any benefit to trigger warnings, and most of the studies they found cite harmful effects.
Most of the studies finding benefits were based on self-reports of students, and cited theoretical frameworks of what triggers might be able to accomplish. Of the positive studies that I was able to find, none actually documented any real-world positive benefits. One of them merely concluded, "Findings did not reach consensus for or against the use of trigger warnings in medical school; however, students emphasized the importance of learning how to cope with distressing material. Trigger warnings may represent a teaching tool to facilitate classroom discussions about the severity of trauma-related material and problem-focused coping strategies."
Other studies have found no benefit to trigger warnings. The review cited one study of trauma survivors that found no benefit to trigger warnings "for trauma survivors, for self-reported participants with PTSD or for participants who qualified for probable PTSD, even when the survivor’s trauma matched the studied content."
The vast majority of the studies that these researchers reviewed actually found that trigger warnings cause harm to students. "Of the 20 articles reviewed, 13 reflect connections between trigger warnings and maladaptive behaviors. These behaviors include avoidance (n = 7), victimization (n = 4), and disempowerment and marginalization (n = 4)." Another study "of 451 trauma survivors found that providing trigger warnings caused survivors to view trauma as more central to their life narrative, potentially causing harm to survivors by increasing the centrality of trauma in their lives."
Apparently loath to give up a cherished technique, the authors of this review nevertheless concluded that trigger warnings can be useful "as one facet of inclusive practice and [trauma-informed care]." The review did not identify any practices that had successfully integrated trigger warnings. Absent some evidence of successful trauma-informed and holistic programs in college, the best evidence available warns youth-serving organizations that "if employed in isolation or in a tokenistic way, as a disingenuous gesture of trauma awareness, trigger warnings can be harmful to students, potentially inflaming existing stressors and exacerbating maladaptive behaviors."