Gruesome photographs on cigarette packages may deliver more effective anti-smoking messages than words, a new analysis finds. 

Researchers reviewed previous studies comparing images to text warnings on cigarette boxes and found pictures commanded more attention, elicited stronger emotional reactions, summoned more negative attitudes and made it more likely that smokers would vow to quit.

“They say a picture is worth a thousand words – that really seems to be the case here,” said lead study author Seth Noar, co-director of the interdisciplinary health communication program at the University of North Carolina at Chapel Hill.

Globally, tobacco kills about six million people a year, and the annual death tally is expected to reach eight million by 2020, according to the World Health Organization. Smoking can cause heart disease and lung cancer, even when exposure is second-hand, and it can lead to asthma and other breathing difficulties in children who live with smokers.

Just 30 countries, representing about 14 percent of the world’s population, require warning images on at least half of the front and back of cigarette packages with anti-smoking messages in the local language, according to the WHO.

In Australia, for example, cigarette packages have graphic images of sick or dying smokers on the wrappers.

To see how well grotesque images on cigarette packages work as a deterrent, Noar and colleagues analyzed data from 37 experiments involving more than 33,000 people. Every study included in the analysis showed participants both words and pictures to measure which approach was better at discouraging smoking.

The studies reviewed were done in 16 different countries, though most were in the U.S., Canada or Germany, and were published between 2000 and 2013.

Relative to text, images convinced people to think more about the effects of smoking, lowered cravings and increased aversion to cigarettes, the analysis found.

Eight of the studies examined whether participants thought the pictures were effective. This subset of experiments found smokers and nonsmokers thought pictures would encourage them not to start smoking or motivate them to cut back and urge others to quit as well.

When the researchers analyzed data across all of these studies, they found pictures were significantly better than text alone at motivating people to avoid cigarette use.

“Smokers know that cigarettes are bad for them, but they likely tune out vague warnings that they have seen for years, such as `smoking causes cancer,’” Noar said by email. “Seeing images of diseased lungs and people suffering from the negative health impacts of smoking appear to affect smokers in ways that simple text-only messages cannot achieve.”

All but one of the studies included in the review lacked data on how the images or texts might impact behavior, the researchers acknowledge in the journal Tobacco Control. The studies also didn’t follow people over long periods of time or measure how repeated exposures to the images might influence behavior, the authors note.

Because smoking is often a social behavior, more research is needed on how social interactions might influence the impact of anti-smoking images on packages, the researchers wrote.

Images may help reach an audience that’s particularly vulnerable – people with lower literacy or education levels, said Jim Thrasher, a researcher in health behavior at the Arnold School of Public Health at the University of South Carolina in Columbia.

“Even among these disadvantaged groups where smoking rates are highest, pictorial warnings are a promising way to stimulate smoking cessation,” Thrasher, who wasn’t involved in the study, said by email.

They may also help young people get the message about smoking, said David Hammond, who researches addiction and cigarette packaging at the University of Waterloo in Ontario, Canada.

“One of the challenges for cigarette warnings is that many of the most severe health consequences don’t appear for a number of years,” Hammond, who wasn’t involved in the study, said by email. “Images help to make these health consequences more salient and real for youth and young adults.”