"I don't think that increased nicotine levels are the reason why I continue to be a smoker," Roberts says. "Nicotine is a very small part of the reason I smoke. It is more the issue of social habits and other habits, and that the oral fixation aspect has much to do with it."
However, Connolly says many smokers may be more hooked on this addictive chemical than they realize.
"People smoke for nicotine whether they admit it or not," he says. "The basis of cigarettes is nicotine delivery; if you take it out, people won't smoke it."
Though the reasons why the tobacco industry might want to intentionally increase the nicotine levels in their products are not entirely clear, public health experts say an increased dose may lead to greater addiction potential.
In short, more nicotine may make it easier for new smokers to get addicted -- and more difficult for seasoned smokers to quit.
"It would appear that the companies are trying to compete by increasing the consumer acceptance of their products," says Dr. Joseph DiFranza, professor of family medicine and community health at the University of Massachusetts Medical School. "Cigarettes with higher nicotine yields are generally rated as more 'satisfying,' meaning that they satisfy the addiction."
"This is further evidence that manufacturers are seeking ways to make their products more addictive," says Dr. Jonathan Klein, at the University of Rochester. "It is particularly concerning for adolescent and young adult smokers, as they are more susceptible to addiction.
"Higher drug levels make continued addiction more likely."
Cummings says that whatever the motivation, the finding of the Harvard study suggests cigarette companies are moving in the wrong direction with regard to consumer health.
"The question that every consumer should be asking is why is the company saying that smoking causes disease and death and nicotine is addictive, but then putting more nicotine in cigarettes?" Cummings asks. "And what the hell is the government doing about it?"