For years, they have been the subject of impassioned academic debate: Trigger warnings. Do they protect people from distress or encourage fragility?

The warnings, which alert individuals to disturbing material, have been talked about, used and promoted on college campuses and elsewhere for more than a decade, but little was known about how well they work. Now, a pair of recent studies suggest that they may have little effect at all.

“Although people were distressed by the negative materials we showed them, they were no more or less distressed if they’d seen a trigger warning first,” said Mevagh Sanson of the University of Waikato in New Zealand, lead author of one study published this month in Clinical Psychological Science, a journal of the Association for Psychological Science.

Individually, the studies are limited, but collectively they offer early signs that the potential benefits — and drawbacks — of the warnings are, in the words of Sanson and her co-authors, trivial at best. Still, experts said, much more study is needed before grand conclusions can be drawn.

“The research is really in its infancy,” said Vaile Wright, director of research and special projects at the American Psychological Association and has treated combat veterans and victims of sexual and domestic violence. “Naturally the research hasn’t really quite caught up to how I think it’s being implemented.”

In a series of experiments, Sanson and her colleagues presented hundreds of students and others recruited online with short stories or video clips, all of which featured negative themes, like child abuse, murder, a car crash or physical abuse. Some participants were presented with trigger warnings and some were not. Some also reported having experienced past trauma, like domestic abuse or witnessing a very bad accident.

In each case, the researchers asked participants about their mood before and after reading the passages or watching the clips. They also measured the distressing effects of the material in several other ways, including how it interfered with the participants’ ability to read and understand a subsequent neutral passage.

What the authors found was that trigger warnings had little effect on participants’ mood, how negatively they rated the material or their ability to later read the neutral passage. “Taken together, our findings show that trigger warnings are at best trivially helpful.”

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 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 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 Cornell philosophy professor, 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.”