When we think about smoking’s addictive qualities, the culprit that most often comes to mind is the infamous stimulant, nicotine. The plethora of patches and chewing gums available on store shelves that are meant to dull that itch attest to how nicotine is the therapeutic target of choice.

Countering this dogma, though, are researchers in New Zealand who have further verified that nicotine is not the only ingredient in tobacco products that makes kicking a smoking habit an uphill battle.

At this week’s Smokefree Oceania conference in Auckland, New Zealand, Penelope Truman of the Institute of Environmental Science and Research (ESR) presented a study that showed how rats exhibited a greater willingness to obtain a dose of smoke from non-nicotinic rolling tobacco compared with doses of nicotine and smoke from factory-made cigarettes that contain nicotine.

Truman, along with researchers from Victoria University, gauged the extent that rats were willing to press a lever to obtain a dose of saline that was infused with either just nicotine or a type of tobacco smoke. Because rats showed a significantly higher willingness to go the distance to get a taste of rolling tobacco smoke, the authors concluded that a substance other than nicotine must be getting them hooked.

“[N]on-nicotinic components have a role in tobacco dependence and…some tobacco products have higher abuse liability, irrespective of nicotine levels,” the study authors concluded.

“This extra chemical is an additional thing that makes smoking harder to give up,” Truman explained to The New Zealand Herald. “This is a formal proof that some tobacco substances are more addictive than nicotine is.” What this specific tobacco component actually is has yet to be identified though.

In light of this finding, the director of Auckland University’s National Institute of Health Innovation, Chris Bullen, suggested the presence of other chemicals in cigarettes that are intended to boost the addictive properties of smoking, regardless of the absence of nicotine.

"It could in part explain why nicotine replacement therapy and any other kinds of products that deliver nicotine as a substitute to mitigate withdrawal and cravings might not be as effective as they could be,” Bullen explained to the Herald.

For example, a 2012 study conducted by the Harvard School of Public Health and the University of Massachusetts found that relapse rates were the same between smokers who used nicotine replacement therapies and those who did not.

Truman and colleagues’ study, Bullen noted to the Herald, could lead to the development of enhanced-effectiveness medications to help smokers quit. “That's the end goal of this kind of research,” he concluded, “to identify what that missing piece could be, and address that with some kind of medication."