The intended message will more likely reach younger adults, or those who might have just picked up the habit, said Joy Schmitz, professor of psychiatry and behavioral sciences at the University of Texas medical school in Houston.
"It might give them pause for concern or contemplation as to their choice of smoking when they see the pretty dramatic scene on the packages," Schmitz said.
But evidence suggests that for message to be effective in the long run, it must not only communicate the danger but also offer ways to help change behavior, Emerson College's Edgar said.
"Simply showing someone that there is a severe outcome or they're personally responsible is not enough. They need to know there's something they can do about it," he said.
"It needs to be combined with the anti-smoking policies, restricting smoking in the environment, as well as promoting effective evidence-based smoking cessation treatments that are available," she said.
Leading cancer groups, including the American Cancer Society, approached the FDA early on in the development of the labels and "were adamant about including the 1-800-Quit-Now number," said Thomas Glynn, director of cancer science and trends at the American Cancer Society.
"To be most effective, these labels need to be paired with an action," Glynn said.
The FDA indicated that the number will be included in the label design.
Although smoking rates have declined overall since the 1960s, health officials noted, that rates have leveled off in the past decade. About 21 percent of U.S. adults, and nearly 20 percent of high school students smoke cigarettes, according to the Centers for Disease Control and Prevention.
The agency's goal is to reduce the 443,000 deaths associated with tobacco use each year.
"Having a coordinated policy, having these warnings, making them so visible, making them real is, in my opinion and in the opinion of the American Cancer Society, going to be a very positive step forward," Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, said when the proposed images were first released.