Smokers who viewed ads featuring reasons why to quit were substantially more likely to quit smoking after the four-week study period, researchers said.
However, ads with messages about how to quit smoking had no effect on an individual's smoking behaviour.
"Why to quit smoking messages are more powerful because those ads typically show graphic portrayals of the health consequences of smoking or feature personal testimonies to evoke emotion," said Jennifer Duke, senior research public health analyst at RTI International, a nonprofit organisation in North Carolina, and co-author of the study.
"Whereas, how to quit messages are designed to increase an individual's belief that he or she can quit," Duke said.
The new research findings are consistent with the results of previous studies; however, this study is unique because it is the first to find that brief exposure to ads containing messages about why to quit smoking that feature strong, negative emotions or graphic images can influence smoking behaviours.
The study examined the effectiveness of various combinations of why to quit and how to quit message strategies in a randomised controlled experiment among a nationally representative sample of 3,000 smokers in the US.
During the four-week study period, participants completed a baseline survey and follow-up interviews at two and four weeks to determine the short-term impact of the ads.
After two weeks, the study found that smokers who viewed ads with messages about why to quit smoking reported increased concern about the health consequences of smoking and greater intentions to quit smoking in the following six months as compared to smokers who did not view the ads.
After four weeks, smokers who viewed ads with messages about why to quit smoking were six to 10 times more likely to have quit smoking as compared to smokers who viewed no ads.
Smokers who only viewed ads about how to quit smoking did not change their smoking habits or intentions to quit at either stage of the study.
The study also found that exposure to a combination of messages about why to quit and how to quit smoking did not improve the impact of the ads more than only viewing ads about why to quit smoking.
"Smokers are more likely to pay attention to graphic or emotional content," Duke said.
"Anti-smoking TV media campaigns should use hard-hitting ads emphasising why to quit smoking because they are effective at increasing cessation over a brief time period," Duke added.