That conclusion was in line with that of another study published this month, in the Journal of Experimental Psychology: Applied, published by the American Psychological Association.

For that study, researchers at Flinders University in Australia recruited 1,600 people online to look at photos that could be interpreted as positive, negative or neutral. They similarly measured mood throughout the experiment and found that while trigger warnings provoked an immediate decrease in mood, they had little other effect — a result that the authors noted was in line with the then-unpublished research conducted by Dr. Sanson and her colleagues.

While preliminary evidence suggests that trigger warnings are neither helpful nor harmful, both studies note that more research needs to be done on how such warnings specifically affect trauma survivors, the population for which they were originally intended.

Psychologists working with traumatized patients have long used the word “"trigger” to refer to sensations or experiences that remind individuals of their original trauma, but trigger warnings are commonly attributed to feminist spaces online.

Those communities began using such warnings years ago to alert readers to sensitive discussions, but it was not until the past decade that the alerts gained more widespread adoption. (For example, Slate, the online magazine, called 2013 the “year of the trigger warning.”) More recently, students on college campuses have increasingly called for their adoption in classrooms and on syllabuses.

Opponents of the idea say that trigger warnings coddle students and allow them to avoid discomforting perspectives. Proponents disagree, arguing that they can help those with a history of trauma avoid potentially disturbing material without banning it outright or brace themselves for it.

“The thought behind trigger warnings isn’t just that these states are highly unpleasant (although they certainly are),” Kate Manne, a professor of philosophy at Cornell University, wrote in The New York Times in 2015. “It’s that they temporarily render people unable to focus, regardless of their desire or determination to do so. Trigger warnings can work to prevent or counteract this.”