One approach to trigger warnings, provided by Karli Cerankowski of Feminist, Gender, and Sexuality Studies at Stanford:
Note: I do not print these statements on my syllabus, but I do state some version or combination of the two statements below in the first couple course sessions. I also sometimes provide a written version in the "policies" section of a course website.
“I will not give trigger warnings for individual readings and assignments, as it is hard to know what will trigger whom. But I want to say something about triggering for the overall course. Course content will address multiple forms of violence, which may include rape, child abuse, physical assault and murder, genocide, as well as systemic violence derived from racism, ethnocentrism, ablism, homophobia/heterosexism, and/or transphobia. Be aware of that, take care of yourself, support each other. This material will push us emotionally, intellectually, and psychically. I want you to understand the difference between feeling bad about something and recognizing your emotional response vs. being triggered, experiencing symptoms of PTSD, flashbacks, or reliving past trauma. If you feel yourself being triggered, you may leave the room without explanation, excuse yourself from a conversation, or contact me about alternative assignments.
Because this is a course in which we will be working with materials in sexuality studies, gender studies, race and ethnicity studies, and disability studies, the assigned readings and film/video viewings may include mature language, racially charged content, sexually explicit materials, visual representations of bodies in various states of dress and/or sexual acts, and descriptions of sexual activity. If you have any personal concerns about viewing or reading such materials, please talk to me individually. Modified or alternative readings can be arranged on an individual basis if necessary. We should all work together to foster a respectful atmosphere for discussion (“safe space, brave space”). If you are feeling triggered by material and do not wish to be present during a particular discussion, you may excuse yourself without need for explanation. I recognize that the theme of this course can bring sensitive topics to the fore, and I hope that you will communicate with me by email or during office hours to work together to address any concerns you might have.”
Here’s another example (from Katie Young’s Policing and Surveillance course syllabus):
Difficult and/or Triggering Topics
The subject matter of this course can be difficult intellectually and emotionally. We are likely to touch on tough topics, including (but not limited to) police brutality, racism, homophobia, sexual assault, abuse, class and gender issues, and more. If you anticipate acute distress as a result of encountering a particular topic, talk to me ahead of time to arrange an alternative written assignment in lieu of your in-class participation. If you become so distressed that you need to leave during class, talk to me afterward and we can arrange an alternate assignment. I will not “warn” students about particular topics, because sensitivity to different topics varies from person to person, and because topics may arise unexpectedly in class discussion. Additionally, as you may know, there is a difference between being triggered (in the sense of post-traumatic stress disorder) and feeling uncomfortable. Feeling uncomfortable (and sometimes even angry or offended) is part of intellectual growth. Feeling triggered or psychologically traumatized is not. Please take care of yourselves and each other, and let me know if I can do anything at all to help.
On Trigger Warnings: A Round Table (Entropy Mag, April 2014)