Lots of countries are starting to put graphic labels on cigarette packaging, including images of rotting teeth, diseased lungs, and facial scars.

Those could help reduce smoking: new research shows that graphic labels increase awareness of the harms of smoking among teenagers and young adults.

The study results, published in the Annals of Behavioral Medicine by Washington State University researchers, support a growing body of evidence indicating that visual warnings aid the prevention, cessation, and maintenance of abstinence of smoking.

How the experiment worked

In the Washington State experiments, smoking and nonsmoking adults between 18 and 25 were shown packages with images emphasizing lung cancer, heart disease, stroke, impotence, eye disease, neck, throat, and mouth cancers, and vascular disease.

Participants were then asked to rate the labels from 1 to 7 based on how much the labels evoked worry or made them feel discouraged from smoking.

Read more: Everything you need to know about e-cigarettes

The combination of images and text provided a significantly more effective discouragement of smoking than the text-only labels with 16 of the 18 images. In response to an image warning the dangers of blindness, for example, respondents rated sensations of "worry" at 4.5 for the graphic and 3.6 for the text alone.

Here's what Renee Magnan, a Washington State assistant professor of psychology, had to say on the study:

Our outcomes suggest that focusing on enhancing understanding and knowledge from smoking warning labels that convey true consequences of smoking may not only influence motivation directly—both in terms of quitting and prevention of smoking—but may actually drive the emotional experience of the label, which we know is an important predictor of motivation.

77 countries now have graphic warning labels — but not the United States

More and more countries are adding graphic warnings to their cigarette packages. The Canadian Cancer Society estimates 77 countries had finalized picture warning requirements by September 2014, up from 55 in 2012. Canada was the first country to impose such requirements.

There's at least some evidence the tactic is working. In a survey conducted after Canada mandated visual warnings in 2001, more than 40 percent of smokers reported that health warnings had motivated them to quit smoking. Fifty-seven percent of smokers said the warnings made them consider quitting, and 34 percent reported they helped them to try to quit.

In the US, efforts to add graphic warning requirements have been slammed by opposition from tobacco companies.

The Tobacco Control Act, passed in 2009, gave the Food and Drug Administration the authority to regulate tobacco products. But in a 2012 decision, a court ruled that the proposed packages violated the First Amendment's free speech protections. The court sent the FDA back to the drawing board to come up with new labels.

Read more: What it would take to rid the world of smoking forever