Recent anti-smoking campaigns have increasingly turned to shocking ads and disturbing pictures to steer people away from cigarettes, but research from the University of Missouri suggests that this tactic might actually backfire.

Researchers showed 49 participants different anti-smoking public service announcements, some of which had “threatening and disgusting” images in them, according to a Missouri press release. The researchers found that participants exposed to PSAs featuring both a threatening message and disgusting images tended to stop mentally processing the images while also lowering their emotional reactions to them. On the basis of these reactions, the researchers believe these types of ads could have a “boomerang effect” on viewers.

However, when the PSAs made use of only threatening messages or disgusting images rather than combining the two, the ads resulted in “greater attention, better memory and a heightened emotional response” from the participants, according to researcher Glenn Leshner.

“We noticed in our collection of anti-tobacco public service announcements a number of ads that contained very disturbing images, such as cholesterol being squeezed from a human artery, a diseased lung, or a cancer-riddled tongue,” Leshner said. “Presumably, these messages are designed to scare people so that they don’t smoke. It appears that this strategy may backfire.”

The report was recently published in Journal of Media Psychology.